Suited for

S pac ewa l k i n g

A Teacher’s Guide with Activities for 

Technology Education, Mathematics, and Science

National Aeronautics

and Space Administration

Education Product

Teachers Grades 5–12
Suited for Spacewalking—A Teacher’s Guide with

Activities for Technology Education, Mathematics,

and Science is available in electronic format through

NASA Spacelink—one of the Agency’s electronic

resources specifically developed for use by the 

educational community.

The system may be accessed at the following address:

http://spacelink.nasa.gov
Suited for Spacewalking

A Teacher’s Guide with Activities for Technology 

Education, Mathematics, and Science

National Aeronautics and Space Administration

Office of Human Resources and Education

Education Division

Washington, DC

Education Working Group

NASA Johnson Space Center

Houston, Texas

This publication is in the Public Domain and is not protected by copyright.

Permission is not required for duplication.

EG-1998-03-112-HQ
Acknowledgments

This publication was developed for the National

Aeronautics and Space Administration by:

Writer/Illustrator:

Gregory L. Vogt, Ed.D.

Crew Educational Affairs Liaison

Teaching From Space Program

NASA Johnson Space Center

Houston, TX

Editor:

Jane A. George

Educational Materials Specialist

Teaching From Space Program

NASA Headquarters

Washington, DC

Reviewers:

Linda Godwin

NASA Astronaut

NASA Johnson Space Center

Joseph J. Kosmo

Senior Project Engineer

EVA and Spacesuit Systems Branch

NASA Johnson Space Center

Philip R. West

Project Manager, EVA Tools 

for the International Space Station

NASA Johnson Space Center

Cathy A. Gardner

Teacher Intern, Teaching From Space

Silbernagel Elementary School

Dickenson, Texas

Deborah A. Shearer

Science Teacher

Zue S. Baales Intermediate School

Friendswood, Texas

Sandy Peck

Clear Creek Independent School District

League City, Texas

Marilyn L. Fowler, Ph.D.

Science Project Specialist

Charles A. Dana Center

University of Texas at Austin 

Jeanne Gasiorowski

Manager, NASA Educator Resource Center

Classroom of the Future

Wheeling Jesuit University

Wheeling, West Virginia 

Dr. Peggy House

Director, The Glenn T. Seaborg 

Center for Teaching and Learning 

Science and Mathematics

Northern Michigan University

Doris K. Grigsby, Ed.D.

AESP Management and Performance 

Specialist for Training

Oklahoma State University

Flint Wild

Technology Specialist

Teaching From Space Program

Oklahoma State University

Patterson A. Biggs

Angelo A. Casaburri

Eva J. Farley

James E. Pratt

Joan Sanders

Aerospace Education Specialists

Oklahoma State University

iii

Suited for Spacewalking—An Activity Guide for Technology Education, Mathematics, and Science, EG- 1 9 9 8 - 0 3 - 1 1 2 - H Q
Table of Contents

National Education Standards. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

Earth and Space . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

The Outer Space Environment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

Spacewalking History . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

The Space Shuttle EMU . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

Working In Space . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31

EVAs on the International Space Station . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37

Future Spacesuits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39

Activities

Designing Spacesuits for Mars . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43

Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44

Design Brief. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47

Interface Control Document (Master) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49

Interface Control Document (Sample) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50

Teacher Tech Briefs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51

Exploration Briefs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63

Idea Bank. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 89

Glossary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 95

References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 97

NASA Educational Resources . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 99

Go for EVA!. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 101

Evaluation Reply Card . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Insert

v

Suited for Spacewalking—An Activity Guide for Technology Education, Mathematics, and Science, EG- 1 9 9 8 - 0 3 - 1 1 2 - H Q
National Education Standards

The activities set forth in this curriculum supplement address national standards for science and mathe m a t i c s , and the universals of tech n o l o gy for tech n o l o gy educa t i on . The matrices that foll ow specifica lly

identify the standards by activity. The standards for science and mathematics in grades 4–8 and 9–12 have

been com b i n e d .

Universals of Technology 

International Technology Education Association, 1996*

*The Standards for Technology Education are still under development

Suited for Spacewalking An Activity Guide for Technology Education, Mathematics, and Science, EG-1998-03-112-HQ • 1
2 • Suited for Spacewalking An Activity Guide for Technology Education, Mathematics, and Science, EG- 1 9 9 8 - 0 3 - 1 1 2 - H Q

National Science Education Standards

National Research Council, 1996 

Grades 4–12
Suited for Spacewalking An Activity Guide for Technology Education, Mathematics, and Science, EG-1998-03-112-HQ • 3

National Mathematics Standards

National Council of Teachers of Mathematics, 1989

Grades 4–12
Suited for Spacewalking An Activity Guide for Technology Education, Mathematics, and Science, EG-1998-03-112-HQ • 5

In t r o d u c t i o n

Sp a c ewalking has ca p t u red the imagination of

g e n e ra t i ons of ch i l d ren and adults since sciencef i c t i on authors first placed their ch a racters on the

M o on . But true spacewalking did not actually begin

until the mid-1960s with the exploits of Alexei A.

Le on ov of the Soviet Union and Edward H.White II

of the United St a t e s . Since those first tentative

p robings outside a space ca p s u l e, a s t ronauts and cosm onauts have logged thousands of hours on extra vehicular activities, and some have even walked on the

s u rface of the Moon . The stories of their missions in

space are fascinating, but just as interesting is the

spacesuit tech n o l o gy that made it possible for them

to “w a l k” in space.

To d ay, spacesuits are used by astronauts on

m a ny missions such as servicing the Hubble Sp a c e

Telescope and re t ri eving satell i t e s . The new

I n t e rn a t i onal Space St a t i on will depend upon astronauts and cosmonauts to conduct over 1,200 hours

of spacewalks over the next seve ral years to assemble

and maintain Space St a t i on com p on e n t s . A l t h o u g h

no firm plans exist, NASA hopes to re t u rn to the

M o on to establish a permanent base and later begin

human surface explora t i on of Mars. E a ch of these

ve n t u res places distinct demands on spacesuits systems and the tools astronauts use.

This publica t i on serves as a guide for tech n o l ogy educa t i on teach e r s . While not specifica lly aimed

at other subject are a s , t e a chers of phys i cal science

and mathematics will find the Explora t i on Bri e fs

and the Idea Bank useful as a source of activity ideas.

The guide begins with brief discussions of the

space env i ron m e n t , the history of spacew a l k i n g,

NASA's current spacesuit, and work that astronauts do

d u ring spacew a l k s . These are foll owed by a tech n o l o gy

e d u ca t i on design brief that ch a llenges students to

design and build a spacesuit pro t o type for an extra t e rre s t rial env i ronment no human has ever visited before .

In the process of doing this, students will have to inve stigate the pro p e rties of that env i ronment and determ i n e

what pro t e c t i ve measures must be taken to permit a

f u t u re explorer to work there safe ly.Once accom p l i s h e d ,

students will choose materials and technologies that ca n

be used for con s t ructing and testing the pro t o typ e .T h e

design brief is foll owed by Te a cher Te ch Bri e fs that 

p rovide a source of ideas on how to build spacesuit test

a p p a ratus and by Explora t i on Bri e fs that provide activi ty fra m ew o rks to help students understand import a n t

topics in spacesuit design.

The guide con cludes with a glossary of term s ,

suggested reading list, NASA educa t i onal re s o u rc e s

i n cluding electronic re s o u rc e s , and an ev a l u a t i on

q u e s t i on n a i re .We would appreciate your assistance in

i m p roving this guide in future editions by com p l e t i n g

the fe e d b a ck question n a i re electron i ca lly or mailing

the form to us.
6 • Suited for Spacewalking An Activity Guide for Technology Education, Mathematics, and Science, EG- 1 9 9 8 - 0 3 - 1 1 2 - H Q

M e a s u r e m e n t

This activity guide makes use of the metric system

for measurement. However, British units for measurement may be listed in materials and tools lists

when particular items are more easily found in

British measurement sizes. The pascal or metric

unit for pressure may be unfamiliar to readers. A

pascal is equal to a force of one newton exerted over

an area of one square meter. Because the pascal is a

relatively small unit, the more convenient unit of

kilopascal (1,000 pascals) is used here instead. To

convert kilopascals to the British-system unit of

pounds per square inch, divide by 6.895.
If we define an astronaut as som e one who

t ra vels through space, eve ryone on Earth is an

a s t ron a u t .E ven though we may be standing still on

E a rth's surf a c e, we are actually tra veling thro u g h

space at speeds of thousands of kilometers per

h o u r. I n d e e d , our planet may be thought of as a

spaceship on a never-ending voy a g e . As "astronauts" tra veling through space on the surface of

E a rt h , we take for granted the complex env i ronment that sustains life . E a rt h’s gra v i t a t i onal attra ct i on holds a dense atmosph e re of nitro g e n , ox y g e n ,

ca rb on diox i d e, and water vapor in a thick enve l o p e

s u r rounding Eart h’s entire surf a c e . The weight of

this atmosph e re exe rts pre s s u re, and its move m e n t s

d i s t ribute heat from the Sun to balance global temp e ra t u re s . Its gases filter out harmful ra d i a t i on and

d i s i n t e g rate all but the largest meteoro i d s . E a rt h’s

a t m o s ph e re is a shell that protects and sustains the

l i fe forms that have ev o lved on its surf a c e . Wi t h o u t

the atmosph e re’s pro t e c t i on , l i fe as pre s e n t ly

k n own would not be possible.

When Earth astronauts leave the surface of

their planet and travel into space, they must carry

some of their environment with them. It must be

contained in a physical shell because their body

masses are too small to hold it in place by gravitational attraction alone. The shell that is used is

called a spacecraft—a rigid collection of metal,

glass,plastic,and composites.Though far simpler in

function than Earth’s environment, a spacecraft's

environment serves well for short missions lasting a

few days or weeks. On some flights, the shell is

deliberately opened and the astronauts pass through

an airlock to venture outside. When doing so, they

must be protected by a still smaller and very spec i a l i zed ve r s i on of their spacecra ft ca lled the

Extravehicular Mobility Unit (EMU).This smaller

spacecraft is composed of a spacesuit with a lifesupport system. It differs from the first spacecraft,

or mother ship, in its anthropomorphous (human)

shape and its flexibility. Astronauts wearing EMUs

Suited for Spacewalking An Activity Guide for Technology Education, Mathematics, and Science, EG-1998-03-112-HQ • 7

Earth and Space

Earth as seen by the crew ofthe Apollo 17 Moon mission.
need to be able to move arms, hands, and legs to

perform an array of tasks in space. They must be

able to operate many types of scientific apparatus,

collect samples, take pictures, assemble equipment

and structures, pilot themselves about, and repair

and service defective or worn-out satellites and

other space hardware. The tasks of astronauts outside their mother ship are called extravehicular

activities, or EVAs.

8 • Suited for Spacewalking An Activity Guide for Technology Education, Mathematics, and Science, EG- 1 9 9 8 - 0 3 - 1 1 2 - H Q
Outer space is just what its name implies. It is

the void that lies beyond the uppermost reaches of

the atmosphere of Earth and between all other

objects in the universe. Although it is a void, outer

space may be thought of as an env i ron m e n t .

Radiation and objects pass through it freely. An

unprotected human or other living being placed in

the outer space environment would perish in a few

brief, agonizing moments.

The principal env i ronmental ch a ra c t e ristic of

outer space is the vacuum, or nearly total absence of

gas molecules. The gra v i t a t i onal attra c t i on of large

bodies in space, s u ch as planets and stars, p u lls gas

molecules close to their surfaces leaving the space

b e tween virt u a lly empty. Some stray gas molecules are

found between these bodies, but their density is so low

that they can be thought of as pra c t i ca lly non e x i s t e n t .

On Earth,the atmosphere exerts pressure in all

directions. At sea level, that pressure is 101 kilopascals. In space, the pressure is nearly zero. With virtually no pressure from the outside, air inside an

unprotected human's lungs would immediately rush

Suited for Spacewalking An Activity Guide for Technology Education, Mathematics, and Science, EG-1998-03-112-HQ • 9

The Outer Space Environment
out in the vacuum of space.Dissolved gases in body

fluids would expand, pushing solids and liquids

apart. The skin would expand much like an inflating balloon. Bubbles would form in the bloodstream and render blood ineffective as a transporter

of oxygen and nutrients to the body’s cell s .

Furthermore, the sudden absence of external pressure balancing the internal pressure of body fluids

and gases would rupture fragile tissues such as

eardrums and capillaries.The net effect on the body

would be swelling, tissue damage, and a deprivation

of oxygen to the brain that would result in unconsciousness in less than 15 seconds.

The temperature range found in outer space

provides a second major obstacle.The sunlit side of

objects in space at Earth's distance from the Sun

can climb to over 120° Celsius while the shaded

side can plummet to lower than minus 100° Celsius.

Maintaining a com f o rtable tempera t u re ra n g e

becomes a significant problem.

Other env i ronmental factors encountered in

outer space incl u d e : m i c ro g ra v i ty, ra d i a t i on of electrica lly charged part i cles from the Su n ,u l t raviolet ra d ia t i on , and meteoro i d s .M e t e o roids are ve ry small bits

of ro ck and metal left over from the form a t i on of the

solar system and from the coll i s i ons of comets and

a s t e ro i d s . Though usually small in mass, these part icles tra vel at ve ry high velocities and can easily penet rate human skin and thin metal. E q u a lly dangero u s

is debris from previous space mission s . A tiny paint

chip tra veling at thousands of kilometers per hour ca n

do substantial damage.

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Suited for Spacewalking An Activity Guide for Technology Education, Mathematics, and Science, EG-1998-03-112-HQ • 1 1

The Extravehicular Mobility Unit worn during

spacewalks by NASA’s Space Shuttle astronauts

represents more than 60 years of development and

testing of pressure suits in the U.S., Russia, France,

Italy, Germany, and other countries. It all began

with high-altitude flyers,and one of the first was an

American, Wiley Post. Post, an aviation pioneer of

the 1930s, was seeking to break high-altitude and

speed records. Post, as well as others, knew that

p ro t e c t i on against low pre s s u re was essential.

T h rough experi e n c e, aviators had learned that

Earth’s atmosphere thins with altitude.

At 5,500 meters, air is on ly one-half as dense as

it is at sea leve l . At 12,200 meters, the pre s s u re is so

l ow and the amount of oxygen is so small that most

living things peri s h . For Wi l ey Post to ach i eve the

altitude re c o rds he sought, he needed pro t e c t i on .

( Pre s s u ri zed airc ra ft cabins had not yet been deve loped.) Po s t’s solution was a suit that could be pre ss u ri zed by his airplane engine’s superch a r g e r.

First attempts at building a pressure suit failed

since the suit became rigid and immobile when

pressurized. Post discovered he couldn’t move inside

the inflated suit, much less work airplane controls.

A later version succeeded with the suit constructed

already in a sitting position. This allowed Post to

place his hands on the airplane controls and his feet

on the rudder bars. Moving his arms and legs was

difficult, but not impossible. To provide visibility, a

viewing port was part of the rigid helmet placed

over Post’s head. The port was small, but a larger

one was unnecessary because Post had only one

good eye!

During the next 30 years,pressure suits evolved

in many ways and technical manufacturing help was

gained from companies that made armor, diving

s u i t s , g a l o s h e s , and even girdles and corsets.

Spacewalking History

Aviation pioneer Wiley Post.
Designers learned in their search for the perfect suit

that it was not necessary to provide full sea-level

pressure. A suit pressure of 24.13 kilopascals (sea

level–101 kilopascals) would suffice quite nicely if

the wearer breathed pure oxygen. Supplying pure

oxygen at this low pressure actually provides the

breather with more oxygen than an unsuited person

breathes at sea level.(Only one-fifth of the air at sea

level is oxygen.)

Va rious techniques were used for con s t ru c t i n g

p re s s u re garm e n t s . Some appro a ches employed a ri g i d

l ayer with special joints of rings or cables or som e

other device to permit limb move m e n t s . Others used

n on - s t re t ch fabrics—laced-up corset fashion .

With the advent of pressurized aircraft cabins,

comfort and mobility in the suit when it was

u n p re s s u ri zed became prime objectives in suit

design.The suit could then be inflated in the event

that the aircraft cabin lost pressure.

Project Mercury

By the time NASA began the Merc u ry

manned space flight program,the best full-pressure

suit design consisted of an inner gas-bladder layer

of neoprene-coated fabric and an outer restraint

layer of aluminized nylon. The first layer retained

pure oxygen at 34.5 kilopascals; the second layer

prevented the first from expanding like a balloon.

This second fabric restraint layer directed the oxygen pressure inward on the astronaut. The limbs of

the suit did not bend in a hinge fashion as do

human arms and legs. Instead, the fabric arms and

legs bent in a gentle curve, which restricted movement. When the astronaut moved one of his arms,

the bending creased or folded the fabric inward near

the joints, decreasing the volume of the suit and

increasing its total pressure slightly. Fortunately for

the comfort of the Mercury astronauts,the Mercury

suit was designed to serve only as a pressure backup

if the spacecraft cabin decompressed. No Mercur y

capsule ever lost pressure during a mission, and the

suits remained uninflated.

1 2 • Suited for Spacewalking An Activity Guide for Technology Education, Mathematics, and Science, EG- 1 9 9 8 - 0 3 - 1 1 2 - H Q

Early spacesuit design.

Project Mercury astronauts.(Front row, left to right) Walter M.Schirra,Jr.,

Donald K.Slayton,John H.Glenn,Jr.,M.Scott Carpenter. (Back row, left

to right) Alan B.Shepard, Jr.,Virgil I. Grissom,L.Gordon Cooper, Jr.
Project Gemini

The six flights of the Merc u ry series were 

f o ll owed by ten flights in the Gemini pro g ra m .

Suit designers were faced with new pro b l e m s . No t

on ly would a Gemini suit have to serve as a pre ss u re backup to the spacecra ft ca b i n , but also as an

e s cape suit if ejection seats had to be fired for an

a b o rted launch and as an EMU for extra ve h i c u l a r

a c t i v i ty. To increase mobility and com f o rt of the

suit for lon g - t e rm wear, designers departed from

the Merc u ry suit con c e p t . Instead of fabric joints,

t h ey chose a con s t ru c t i on that employed a bladder

re s t rained by a net. The bladder was an anthro p om o rph i ca lly shaped layer of neopre n e - c o a t e d

nyl on . That was cove red in turn with a layer of

Te f l on®-coated nyl on netting. The netting, s l i g h tly smaller than the pre s s u re bladder, limited inflat i on of the bladder and retained the pre s s u re load

in mu ch the same way automobile tires retained the

load in inner tubes in the days before tubeless tire s .

The new spacesuit fe a t u red improved mobility in

the shoulders and arms and was more com f o rt a b l e

when worn unpre s s u ri zed during space flights lasting as long as 14 days .

The first Gemini astronaut to leave his vehicle

(“go EVA”) was Edward White, II. White exited

from the Gemini 4 space capsule on June 3,1965—

just a few months after Leonov made the first

Soviet spacewalk. For a half-hour, White tumbled

and rolled in space, connected to the capsule only by

an oxygen-feed hose that served secondary functions as a tether line and a communication link with

the capsule. Although the term “spacewalk” was

coined for the Gemini program, no actual walking

was involved.On his spacewalk, White used a small

hand-held pro p u l s i on gun for maneuve ring in

space. When he pulled a trigger, the gun released

jets of nitrogen that propelled him in the opposite

direction.It was the first personal maneuvering unit

used in space.

Upon completion of the Gemini program,

NASA astronauts had logged nearly 12 additional

hours of EVA experience. Approximately one-half

of that time was spent merely standing up through

the open hatch.

One of the most important lessons learned

during the Gemini program was that EVAs were

not as simple as they looked. Moving around in

space required a great deal of work.The work could

be lessened, h ow eve r, by extensive training on

E a rt h . The most effe c t i ve training took place

underwater. Wearing specially-weighted spacesuits

while in a deep tank of water gave later Gemini

crew members adequate practice in maneuvers they

would soon perform in space. It was also learned

that a better method of cooling the astronaut was

required.The gas cooling system could not remove

heat and moisture as rapidly as the astronaut produced them, and the inside of the helmet visor

quickly fogged over making it difficult to see.

Project Apollo

Following Gemini, the Apollo program added

a new dimension in spacesuit design because actual

spacewalks (on the surface of the Moon) were now

Suited for Spacewalking An Activity Guide for Technology Education, Mathematics, and Science, EG-1998-03-112-HQ • 1 3

Edward H. White’s historic spacewalk.
to occur for the first time. As with Merc u ry and

Gemini space garm e n t s , Ap o llo suits had to serve

as a backup pre s s u re system to the space ca p s u l e .

Besides all owing flexibility in the shoulder and arm

a re a s , t h ey also had to permit movements of the

legs and waist. A s t ronauts needed to be able to

bend and stoop to pick up samples on the Moon .

Suits had to function both in micro g ra v i ty and in

the one-sixth gra v i ty of the Moon's surf a c e .

Fu rt h e rm o re, when walking on the Moon , Ap o ll o

a s t ronauts needed the flexibility to roam fre e ly

without dragging a cumbersome com b i n a t i on 

oxygen line and tether. A self-contained port a b l e

l i fe - s u p p o rt system was needed.

The Apollo spacesuit began with a garment

that used water as a coolant. The garment, similar

to long johns but laced with a network of thinw a lled plastic tubing, c i rculated cooling water

around the astronaut to prevent overheating. A

multi-layered pressure garment was worn on top of

the cooling suit. The innermost layer of this garment was a comfort layer of lightweight nylon with

fabric ventilation ducts. On top of this was a layer

of neoprene-coated nylon surrounded by a nylon

restraint layer. This layer contained the pressure

inside the suit. Improved mobility was achieved by

bellow-like joints of formed rubber with built-in

restraint cables at the waist, elbows, shoulders,

wrist, knees, and ankles. On top of the pressure

layer were five layers of aluminized Mylar® for heat

protection, mixed with four spacing layers of nonwoven Dacron®. Above these were two layers of

Kapton and beta marquisette for additional thermal

p ro t e c t i on and a nonflammable and abra s i on -

protective layer of Teflon®-coated filament beta

cloth. The outermost layer of the suit was white

Teflon® cloth.The last two layers were flame resistant. In total, the suit layers provided pressure,

s e rved as a pro t e c t i on against heat and cold, and protected the wearer against microm e t e o roid impacts

and the wear and tear of walking on the Moon .

Capping off the suit was a communications

headset and a clear polycarbonate-plastic pressure

helmet. Slipped over the top of the helmet was an

a s s e m b ly consisting of sun-filtering visors and

adjustable blinders for sunlight protection. The

final items of the Apollo spacesuit were lunar protective boots, a portable life-support system, and

custom-sized gloves with molded silicone-rubber

fingertips that provided some degree of fingertip

sensitivity in handling equipment.

The life - s u p p o rt sys t e m , a back p a ck unit,

p rovided oxygen for breathing and pre s s u ri za t i on ,

water for cooling, and radio com mu n i ca t i ons for

lunar surface exc u r s i ons lasting up to eight hours.

Fu rt h e rm o re, b a ck inside the lunar lander the life -

s u p p o rt system could be re charged with more ox y g e n

and battery power for additional Moonw a l k s .

During the Apollo program, 12 astronauts

spent a total of 161 hours of EVA on the Moon’s

surface. Additional EVAs were spent in microgravity while the astronauts were in transit from the

Moon to Earth. During a total of four hours, one

1 4 • Suited for Spacewalking An Activity Guide for Technology Education, Mathematics, and Science, EG- 1 9 9 8 - 0 3 - 1 1 2 - H Q

Astronauts Harrison H.Schmitt (foreground) and Eugene A.Cernan practice

sampling lunar sediment in a simulated Moon site constructed at the Kennedy

Space Center in Florida.The Apollo 17 astronauts were the last humans to

walk on the Moon.
astronaut, the command module pilot, left the capsule to retrieve photographic film. There was no

need for the portable life-support system away from

the Moon, as those astronauts were connected to

the spacecraft by umbilical tether lines supplying

them with oxygen.

Skylab

NASA’s next experience with EVAs came during the Skylab program and convincingly demonstrated the need for astronauts on a spacecraft.

Spacesuited Skylab astronauts literally saved the

Skylab program.

Skylab was NASA’s first space station. It was

launched in 1973, six months after the last Apollo

M o on landing. Trouble developed during the

launch when a micrometeoroid shield ripped away

from the station’s outer surface. This mishap triggered the premature deployment of two of the six

solar panels, resulting in one being ripped away by

atmospheric friction. The second was jammed in a

partially opened position by a piece of bent metal.

In orb i t , Sk ylab re c e i ved insufficient electri ca l

power from the remaining solar panels: the station

was overheating because of the missing shield.

Instead of scrapping the mission, NASA assigned

the first three-astronaut crew the task of repairing

the crippled station.While still on board the Apollo

c ommand module, Paul Weitz unsuccessfully

attempted to free the jammed solar panel as he

extended himself through the open side hatch. On

board Skylab, the crew poked an umbrella-like

portable heat shield through the scientific airlock to

cover the area where the original shield was torn

away. Later, on an EVA, the metal holding the

jammed solar arrays was cut, and the panel was

freed to open.During an EVA by the second Skylab

Suited for Spacewalking An Activity Guide for Technology Education, Mathematics, and Science, EG-1998-03-112-HQ • 1 5

John W. Young,Commander ofthe Apollo 16 lunar landing mission to the Descartes region,salutes the American flag as he jumps upward in the one-sixth Earth

gravity on the Moon.Behind him are the lunar module “Orion” and the lunar roving vehicle.
1 6 • Suited for Spacewalking An Activity Guide for Technology Education, Mathematics, and Science, EG- 1 9 9 8 - 0 3 - 1 1 2 - H Q

crew, an additional portable heat shield was erected

over the first.

The Skylab EMU was a simplified version of

the Apollo Moon suits. There was no need for the

p o rtable life - s u p p o rt system because the crew

member was attached to the station by an umbilical

tether that supplied oxygen and cooling water. An

a s t ronaut life - s u p p o rt assembly, c onsisting of a

pressure-control unit and an attachment for the

tether, was worn on the chest, and an emergency

oxygen package containing two supply bottles was

attached to the right upper leg. A simplified visor

assembly was worn over the pressure helmet. Lunar

protective boots were not needed.Skylab astronauts

logged 17.5 hours of planned EVA for film and

experiment retrieval and 65 hours of unplanned

EVA for station repairs.
Suited for Spacewalking An Activity Guide for Technology Education, Mathematics, and Science, EG-1998-03-112-HQ • 1 7

As NASA changed from launching astronauts

on expendable rockets to the Space Shuttle system

with its reusable orbiter and solid rocket boosters,

spacesuit engineers began deve l o pment of a

reusable EMU. Previously, all spacesuits were onetime garments. Spacesuits were custom-built to

each astronaut’s body size. In the Apollo program,

for example, e a ch astronaut had three custom

suits—one for flight, one for training, and one for

flight backup. Shuttle suits, however, are tailored

from a stock of standard-size parts to fit astronauts

with a wide range of measurements.

In con s t ructing the Shuttle spacesuit, d eve l o pers were able to con c e n t rate all their designs tow a rd

a single function — going EVA . Suits from earl i e r

manned spaceflight pro g rams had to serve mu l t i p l e

f u n c t i on s . T h ey had to provide backup pre s s u re in

case of cabin pre s s u re failure and, on Gemini 

m i s s i on s , p ro t e c t i on if ejection became necessary

d u ring launch .T h ey also had to provide an env i ronment for EVA in micro g ra v i ty and in low gra v i ty

while walking on the Moon (Ap o llo mission s ) . Su i t s

w e re worn during lift off and re e n t ry and had to be

c om f o rtable under the high-g forces experi e n c e d

d u ring accelera t i on and decelera t i on . Shuttle suits

a re worn on ly when it is time to ve n t u re outside the

o rbiter ca b i n . At other times, c rew members wear

c om f o rtable shirts and slack s , or short s . For launch

The Space Shuttle Extravehicular Mobility Unit (EMU)
and reentry, special orange-colored flight suits with

helmets are worn.

Many Layers

The Shuttle EMU has 14 layers to pro t e c t

a s t ronauts on EVA s . The inner layers com p rise the 

l i q u i d - c o o l i n g - a n d - ve n t i l a t i on garm e n t . First com e s

a liner of Nyl on tricot over which is a layer of spandex fabric laced with plastic tubing. Next comes the

p re s s u re bladder layer of urethane-coated nyl on

and fabric layer of pre s s u re - re s t raining Dacron ® .

A b ove the bladder and re s t raint layer is a liner of

Ne o p rene coated Nyl on Ripstop. This is foll ow e d

by a seve n - l ayer thermal microm e t e o roid garm e n t

of aluminized Myl a r ® , laminated with Dacron ®

s c ri m . The outer layer of the suit is made of Ort h o -

Fa b ric which consists of a blend of Gort e x ® ,

K evl a r ® , and Nomex® materi a l s .

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1. Liquid Cooling and Ventilation

Garment Liner (Nylon tricot)

2 . Liquid Cooling and Ve n t i l a t i on

G a rment Liner Outer Laye r

( Nyl on / Sp a n d e x )

3 . Liquid Cooling and Ve n t i l a t i on

G a rment Liner Water Tra n s p o rt

Tu b i n g

4 . Pre s s u re Garment Bladder 

( Urethane Coated Nyl on )

5 . R e s t raint (Dacron®)

6 . T h e rmal Microm e t e o ro i d

G a rment Liner (Ne o p re n e

Coated Nyl ong Ripstop)

7–13. Thermal

Micrometeoroid

Garment Liner

(Multi-layered

Insulation—

Aluminized

Mylar®)

14. Thermal

Micrometeoroid

Garment Cover

(Ortho-Fabric)
Shuttle EMU End Items

The Shuttle extra vehicular mobility unit

(EMU) consists of 18 separate items. Fully assembled, the Shuttle EMU becomes a nearly complete

short-term spacecraft for one person. It provides

pressure, thermal and micrometeoroid protection,

oxygen, cooling water, drinking water, food, waste

collection,(including carbon dioxide removal),electrical power, and communications.The EMU lacks

only maneuvering capability, but this capability can

be added by fitting a gas jet-propelled Simplified

Aid for Extravehicular Activity Rescue (SAFER)

over the EM U’s pri m a ry life - s u p p o rt sys t e m . O n

E a rt h , the suit and all its part s , f u lly assembled but

without SAFER, weighs about 113 kilogra m s .

O rbiting above Earth it has no weight at all . It does,

h ow eve r, retain its mass in space, which is felt as

resistance to a change in motion.

1. Primary Life-Support System (PLSS)

Self-contained backpack unit containing an oxygen

supply, carbon-dioxide-removal equipment, caution

and warning system,electrical power, water-cooling

equipment, ventilating fan, machinery, and radio.

2 . D i s p l a ys and Control Module (DC M )

Chest-mounted con t rol module containing all

c on t ro l s , a digital display, the external liquid, g a s ,

and electri cal interf a c e s . The DCM also has the

p ri m a ry purge valve for use with the Se c on d a ry

Oxygen Pa ck .

3 . EMU El e c tri cal Harness (EEH )

A harness worn inside the suit to provide bioins t ru m e n t a t i on and com mu n i ca t i ons con n e c t i ons to

the PLSS.

4. Secondary Oxygen Pack (SOP)

Two oxygen tanks with a 30-minute emergency

supply combined,valve, and regulators.The SOP is

attached to the base of the PLSS. The SOP can be

removed from the PLSS for ease of maintenance.

5. Service and Cooling Umbilical (SCU)

Connects the orbiter airlock support system to the

EMU to support the astronaut before EVA and to

provide in-orbit recharge capability for the PLSS.

Suited for Spacewalking An Activity Guide for Technology Education, Mathematics, and Science, EG-1998-03-112-HQ • 1 9
The SCU contains lines for power, communicat i on s , oxygen and water re ch a r g e, and water

drainage. The SCU conserves PLSS consumables

during EVA preparation.

6.Battery

Battery that supplies electrical power for the EMU

during EVA.The battery is rechargeable in orbit.

7. Contaminant Control Cartridge (CCC)

Cleanses suit atmosphere of contaminants with an

integrated system of lithium hydroxide, activated

charcoal, and a filter contained in one unit. The

CCC is replaceable in orbit.

8. Hard Upper Torso (HUT)

Upper torso of the suit, c omposed of a hard fiberglass shell . It provides stru c t u ral support for

mounting the PLSS, DC M , a rm s , h e l m e t , I n - Su i t

Drink Bag, EEH , and the upper half of the waist

cl o s u re . The HUT also has prov i s i ons for mounting a mini-work s t a t i on tool ca r ri e r.

9. Lower Torso

Spacesuit pants, boots, and the lower half of the

closure at the waist.The lower torso also has a waist

bearing for body rotation and mobility, and D rings

for attaching a safety tether.

10. Arms (left and right)

Shoulder joint and shoulder bearing, upper arm

bearings, elbow joint, and glove-attaching closure.

11. EVA Gloves (left and right)

Wrist bearing and disconnect, wrist joint, and fingers.The gloves have loops for attaching tethers for

restraining small tools and equipment. Generally,

crew members also wear thin fabric comfort gloves

with knitted wristlets under the EVA gloves.

2 0 • Suited for Spacewalking An Activity Guide for Technology Education, Mathematics, and Science, EG- 1 9 9 8 - 0 3 - 1 1 2 - H Q

Reference Numbers 8–11.

Hard Upper

Torso underneath fabric

Lower Torso
12.Helmet

Plastic pressure bubble with neck disconnect ring

and ventilation distribution pad. The helmet has a

backup purge valve for use with the secondary oxygen pack to remove expired carbon dioxide.

1 3 . Liquid Cooling-and-Ve n ti l a tion Garm e n t

(LCVG)

Long underwear-like garment worn inside the

pressure layer. It has liquid cooling tubes, gas ventilation ducting, and multiple water and gas connectors for attachment to the PLSS via the HUT.

14.Maximum Absorption Garment (MAG)

An adult-sized diaper with extra absorption material added for urine collection.

15. Extravehicular Visor Assembly (EVA)

Assembly containing a metallic-gold-covered Sunfiltering visor, a clear thermal impact-protective

visor, and adjustable blinders that attach over the

helmet. In addition, four small “head lamps” are

mounted on the assembly; a TV camera-transmitter

may also be added.

16.In-Suit Drink Bag (IDB)

Plastic water-filled pouch mounted inside the

HUT. A tube projecting into the helmet works like

a straw.

Suited for Spacewalking An Activity Guide for Technology Education, Mathematics, and Science, EG-1998-03-112-HQ • 2 1
17.Communications Carrier Assembly (CCA)

Fabric cap with built-in earphones and a microphone for use with the EMU radio.

18.Airlock Adapter Plate (AAP)

Fixture for mounting and storing the EMU inside

the airlock and for use as an aid in donning the suit.

Putting on the EMU

Putting on a Shuttle EMU is a relatively simple operation that can be accomplished in a matter

of about 15 minutes.However, the actual process of

preparing to go EVA takes much longer. When

w o rking in the Shuttle ca b i n , c rew members

breathe a normal atmospheric mix of nitrogen and

oxygen at 101 kilopascals. The suit’s atmosphere is

pure oxygen at 29.6 kilopascals. A rapid drop from

the cabin pressure to the EMU pressure could result

in a debilitating ailment that underwater divers

sometimes experience—the bends. The bends, also

known as caisson disease, are produced by the formation and expansion of nitrogen gas bubbles in

the bloodstream when a person breathing a normal

air mixture at sea-level pressure is exposed to a

rapid drop in external pressure. In severe cases, the

bends are characterized by pains in the joints,

cramps, paralysis, and eventual death if not treated

by gradual recompression.To prevent an occurrence

of the bends, crew members intending to go EVA

spend a period of time prebreathing pure oxygen.

During that time, nitrogen gas in the bloodstream

is replaced by pure oxygen.

Prior to prebreathing, the atmospheric pressure

of the entire orbiter cabin is depressed from the

normal 101 kilopascals to 70.3 pascals while the

p e rcentage of oxygen is slightly incre a s e d .

Prebreathing begins when the crew members who

plan to go EVA don a mask connected to an oxygen

supply. A short hose permits them to continue their

EVA preparations during this period.The length of

time for cabin decompression and the time for 

prebreathing is related. Without any cabin decompression, prebreathing must last at least four hours.

A prebreathe of 30 minutes is safe providing cabin

decompression takes place at least 24 hours before

the exit into space.

By now, much of the dissolved nitrogen gas has

been cleared from the EVA crew members,and they

can remove their helmets. Later, when they don

their spacesuits and seal the helmets, an additional

30 to 40 minutes of pure oxygen prebreathing takes

place before the suits are lowered to their operating

pressure of 29.6 kilopascals.

Most of the EM U - d onning process takes

place inside the airl o ck . The airl o ck is a cyl i n d ri ca l

chamber located on the orb i t e r’s mid-deck . O n e

h a t ch leads from the middeck into the airl o ck ,a n d

a second hatch leads from the airl o ck out to the

u n p re s s u ri zed payload bay.

Before entering the hatch, but following their

initial prebreathing, the crew members put on the

m a x i mum absorb e n cy garment (MAG ) . T h e

MAG is an adult-size diaper.

2 2 • Suited for Spacewalking An Activity Guide for Technology Education, Mathematics, and Science, EG- 1 9 9 8 - 0 3 - 1 1 2 - H Q
Next comes the Liquid Cooling-and-Ve n t i l a t i on

G a rment (LC VG ) . The LC VG has the genera l

a p p e a rance of long underw e a r. It is a one-piece suit

with a zippered fron t , made of stre t chable spandex

f a b ric laced with 91.5 meters of plastic tubing. Wh e n

the EMU is com p l e t e ly assembled, cooling and 

ve n t i l a t i on become significant pro b l e m s . Body heat,

c ontaminant gases, and perspira t i on —a ll waste

p ro d u c t s — a re contained by the insulation and pre ss u re layers of the suit and must be re m ove d .C o o l i n g

of the crew member is accomplished by circ u l a t i n g

ch i lled water through the tubes. C h i lling the water

is one of the functions of the Pri m a ry Life - Su p p o rt

System (PLSS). The PLSS device for water cooling

and the tubing system are designed to provide cooling for phys i cal activity that generates up to tw o

m i ll i on joules of body heat per hour, a rate that is

c on s i d e red “e x t re m e ly vigo ro u s . ” ( Ap p rox i m a t e ly

160 joules are released by burning a piece of

n ew s p rint one centimeter square.) Ducting attach e d

to the LC VG ventilates the suit by drawing ve n t ilating oxygen and expired ca rb on dioxide from the

s u i t’s atmosph e re into the PLSS for puri f i ca t i on and

re c i rc u l a t i on . Body perspira t i on is also drawn away

f rom the suit by the venting system and re cycled in

the water cooling sys t e m . The intakes are loca t e d

near the hands and feet of the suit. Du c t s , ru n n i n g

a l ong the arms and legs on the back of the LC VG

ch a n n e l , the ve n t i l a t i on gases to a circular junction

on the back of the LC VG and into the torso ve n t

d u c t . From there, the gases are re t u rned to the PLSS

via the LCCGV multiple water con n e c t o r. Pu ri f i e d

oxygen from the PLSS reenters the suit thro u g h

another duct, mounted in the back of the helmet,

that directs the flow over the astron a u t’s face to

c omplete the circ u i t .

The EMU electrical harness is attached to the

HUT and provides biomedical and communications hookups with the PLSS. The biomedical

hookup monitors the heart rate of the crew members, and this information is radioed via a link with

the orbiter to Mission Control on Earth. Voice

communications are also carried on this circuit.

Ne x t , s eve ral simple tasks are perf o rm e d .

Antifog compound is rubbed on the inside of the

helmet. A wrist mirror and a small spiral-bound 

27-page checklist are put on the left arm of the

upper torso. The wrist mirror was added to the suit

because some of the knobs on the front of the displays and control module are out of the vision range

of the crew member. The mirror permits the knob

Suited for Spacewalking An Activity Guide for Technology Education, Mathematics, and Science, EG-1998-03-112-HQ • 2 3

Spacesuit technician prepares to put on the Space Shuttle EMU by first donning the Liquid Cooling-and-Ventilation garment.
settings to be read. Setting numbers are written

backwards for ease of reading in the mirror.

Another task at this time is to insert a food bar

and a water-filled In-Suit Drink Bag (IDB) inside

the front of the HUT. The food bar of compressed

fruit,grain,and nuts is wrapped in edible rice paper,

and its upper end extends into the helmet area near

the crew member’s mouth. When hungry, the crew

member bites the bar and pulls it upward before

breaking off a piece to chew. In that manner, a small

piece of the bar remains extended into the helmet

for the next bite.It is necessary to eat the entire bar

at one time, because saliva quickly softens the protruding food bar, making it mushy and impossible

to break off. The IDB is placed just above the bar.

Two sizes of bags are available and the one chosen

is filled with water from the water supply of the

orbiter's galley prior to entry into the airlock. The

largest bag contains nearly 1 liter of water. A plastic

tube and valve assembly extends up into the helmet

so that the crew member can take a drink whenever needed.Both the food bar and drink bag are held

in place by Velcro attachments.

During EVAs, the crew members may need

additional lighting to perform their tasks. A lightbar attachment (helmet-mounted light array) is

placed above the helmet visor assembly. Small builtin flood lamps provide illumination to places that

sunlight and the regular payload bay lights do not

reach. The EVA light has its own battery system

and can be augmented with a helmet-mountable

television camera system with its own batteries and

radio frequency transmitter. The camera’s lens system is about the size of a postage stamp. Through

this system, the crew remaining inside the orbiter

and the mission controllers on Earth can get an

astronaut’s eye view of the EVA action. During

complicated EVAs, viewers may be able to provide

helpful advice for the tasks at hand.

Next, the Communications Carrier Assembly

(CCA), or “Snoopy cap,” is connected to the EMU

electrical harness and left floating above the HUT.

The CCA earphones and microphones are held by

a fabric cap. After the crew member dons the EMU,

the cap is placed on the head and adjusted.

When the tasks preparatory to donning the

suit are completed,the lower torso, or suit pants,are

pulled on.The lower torso comes in various sizes to

meet the varying size requirements of different

astronauts.It features pants with boots and joints in

the hip, knee, and ankle, and a metal body-seal closure for connecting to the mating half of the ring

mounted on the hard upper torso. The lower torso’s

waist element also contains a large bearing. This

gives the crew member mobility at the waist, permitting twisting motions when the feet are held in

workstation foot restraints.

Joints for the lower and upper torsos re p re s e n t

an important advance over those of prev i o u s

s p a c e s u i t s . E a rlier joint designs consisted of hard

ri n g s , b e ll ows-like bends in the pre s s u re bladder,

or cable- and pull ey-assisted fabric joints. T h e

Shuttle EMU joints maintain nearly constant 

volume during bending. As the joints are bent,

re d u c t i ons in volume along the inner arc of the

bend are equalized by increased volume along the

outer arc of the bend.

Long before the upper half of the EMU is

d on n e d , the airl o ck ’s Se rvice and Cooling Umbilica l

(SCU) is plugged into the Displays and Con t ro l

Module Panel on the front of the upper torso. Fi ve

c on n e c t i ons within the umbilical provide the suit

with cooling water, ox y g e n , and electri cal pow e r

f rom the Shuttle itself. In this manner, the con s u mables stored in the Pri m a ry Life - Su p p o rt Sys t e m

w i ll be con s e rved during the lengthy pre b re a t h i n g

p e ri o d . The SCU also is used for battery and consumable re charging between EVA s .

The airl o ck of the Shuttle orbiter is on ly 1.6

meters in diameter and 2.1 meters high on the inside.

When two astronauts pre p a re to go EVA , the space

inside the airl o ck becomes crowd e d . For storage purposes and as an aid in donning and doffing the

EM U, e a ch upper torso is mounted on airl o ck

adapter plates. Adapter plates are bra ckets on the airl o ck wall for supporting the suits’ upper torsos.

2 4 • Suited for Spacewalking An Activity Guide for Technology Education, Mathematics, and Science, EG- 1 9 9 8 - 0 3 - 1 1 2 - H Q
With the lower torso donned and the orbiter

p roviding consumables to the suits, e a ch crew

member “dives” with a squirming motion into the

upper torso.To dive into it,the astronaut maneuvers

under the body-seal ring of the upper torso and

assumes a diving position with arms extended

upward. Stretching out, while at the same time

aligning arms with the suit arms, the crew member

slips into the upper torso. As two upper and lower

body-seal closure rings are brought together, two

connections are made. The first joins the cooling

water-tubing and ventilation ducting of the LCVG

to the Primary Life-Support System. The second

connects the biomedical monitoring sensors to the

EMU electrical harness that is connected to the

PLSS. Both systems are turned on, and the crew

member then locks the two body-seal closure rings

together, usually with the assistance of another crew

member who remains on board.

One of the most important features of the

upper half of the suit is the HUT, or Hard Upper

Torso. The HUT is a hard fiberglass shell under the

fabric layers of the thermal-micrometeoroid garment. It is similar to the breast and back plates of a

suit of armor. The HUT provides a rigid and controlled mounting surface for the Primary LifeSupport System on the back and the Displays and

Control Module on the front.

In the past, d u ring the Ap o llo Moon mission s ,

d onning suits was a ve ry lengthy process because the

l i fe - s u p p o rt system of those suits was a separate item.

B e cause the Ap o llo suits were worn during launch

and landing and also as ca b i n - p re s s u re back u p s , a

HUT could not be used. It would have been mu ch

too uncom f o rtable to wear during the high accelerat i ons and decelera t i ons of lift-off and re e n t ry. T h e

l i fe - s u p p o rt system had to be attached to the suit

inside the lunar module. A ll con n e c t i ons betw e e n

PLSS and the Ap o llo suit were made at that time

a n d , with two astronauts working in cramped quart e r s , p re p a ring for EVA was a difficult pro c e s s . T h e

Shuttle suit HUT eliminates that lengthy pro c e d u re

b e cause the PLSS is already attach e d . It also eliminates the exposed and vulnerable ve n t i l a t i on and life -

s u p p o rt hoses of earlier EMU designs that could

b e c ome snagged during EVA .

The last EMU gear to be donned includes eyeglasses if needed, the com mu n i ca t i ons ca r ri e r

assembly (CCA), comfort gloves, the helmet with

lights and optional TV, and EVA gloves. The two

gloves have fingertips of silicone rubber that permit

some degree of sensitivity in handling tools and

other objects. Metal rings in the gloves snap into

rings in the sleeves of the upper torso. The rings in

the gloves contain bearings to permit rotation for

added mobility in the hand area. The connecting

ring of the helmet is similar to the rings used for the

body-seal closure. Mobility is not needed in this

ring because the inside of the helmet is large

enough for the crew member’s head to move

around. To open or lock any of the connecting

rings, one or two sliding, rectangular-shaped knobs

are moved to the right or the left. When opened,

the two halves of the connecting rings come apart

easily. To close and lock, one of the rings slides part

way into the other against an O-ring seal.The knob

is moved to the right, and small pins inside the

outer ring protrude into a groove around the inside

ring, thereby holding the two together.

All suit openings have locking provisions that

require a minimum of three independent motions

to open.This feature prevents any accidental opening of suit connections.

With the donning of the helmet and gloves,

the spacesuits are now sealed off from the atmosphere of the air lock. The crew members are being

supported by the oxygen, electricity, and cooling

water provided by the orbiter. A manual check of

suit seals is made by pressurizing each suit to 29.6

kilopascals d.(The “d” stands for differential,meaning greater than the air lock pressure.) Inside the air

lock, the pressure is either 70.3 or 101 kilopascals.

The suit’s pressure is elevated an additional 29.6

kilopascals, giving it a pressure differential above

the air lock pressure. Once pressure reaches the

desired level, the oxygen supply is shut off and the

Suited for Spacewalking An Activity Guide for Technology Education, Mathematics, and Science, EG-1998-03-112-HQ • 2 5
digital display on the chest-mounted control module is read. To assist in reading the display, an

optional Fresnel lens inside the space helmet may

be used to magnify the numbers. Some leakage of

spacesuit pressure is normal. The maximum allowable rate of leakage of the Shuttle EMU is 1.38

kilopascals per minute, and this is checked before

the suit is brought back down to air lock pressure.

As the suit pre s s u re is elev a t e d ,c rew members may

e x p e rience discom f o rt in their ears and sinus ca v i t i e s .

T h ey compensate for the pre s s u re change by swall owi n g, y a w n i n g, or pressing their noses on an option a l

s p onge mounted to the left on the inside of the helmet

ri n g. Attempting to blow air through the nose when

p ressing the nose on the sponge forces air inside the ears

and sinus cavities to equalize the pre s s u re .

During the next several minutes the two spacesuits are purged of any oxygen/nitrogen atmosphere

remaining from the cabin;this is replaced with pure

oxygen. Additional suit checks are made while the

final oxygen prebreathe takes place.

The inner door of the air lock is sealed,and the

air lock pre s s u re bleed-down begins. A small

depressurization valve in the air lock latch is opened

to outside space, permitting the air lock atmosphere

to escape.While this is taking place the EMU automatically drops its own pressure to 66.9 kilopascals

and leak checks are conducted. Failure of the leak

test would require repressurizing the air lock, permitting the EVA crew to reexamine the seals of

their suits.

Final depressurization is begun by opening the

air lock depressurization valve. The outer air lock

hatch is then opened and the suited astronauts prepare to pull themselves out into the payload bay. As

a safety measure, they tether themselves to the

orbiter to prevent floating away as they move from

place to place by hand holds. It is at this point that

they disconnect the orbiter Service and Cooling

Umbilical from the EMU. The PLSS begins using

its own supply of oxygen, cooling water, and electricity. The astronauts pull themselves through the

outer air lock hatch, and the EVA begins.

The Primary and Secondary

Life-Support Systems

A s t ronauts experienced their first real fre e d om

while wearing spacesuits during the Ap o ll o

M o onwalk EVA s , b e cause of a portable life - s u pp o rt system worn on their back s . A ll other EVA s

up to that time were tied to the spacecra ft by the

u m b i l i cal-tether line that supplied oxygen and kept

c rew members from dri fting away. In one sense, t h e

tether was a leash, b e cause it limited move m e n t s

a w ay from the spacecra ft to the length of the tethe r. On the Moon , h ow eve r, a s t ronauts were not

h a m p e red by a tether and, in the later mission s ,

w e re permitted to dri ve their lunar rovers up to 10

k i l ometers away from the lander. (That distance

limit was imposed as a safe ty measure .It was determined that 10 kilometers was the maximum distance an astronaut could walk back to the lander if

a lunar rover ever broke dow n . )

Space Shuttle astronauts have even gre a t e r

f re e d om than the Ap o llo lunar astronauts beca u s e

their EVAs take place in the micro g ra v i ty env i ronment of space. T h ey do employ tethers when EVA s

center in and about the Sh u t t l e’s payload bay, b u t

those tethers act on ly as safe ty lines and do not

p rovide life support . Fu rt h e rm o re, the tethers ca n

be moved from one loca t i on to another on the

o rbiter along a slide wire, p e rmitting even gre a t e r

distances to be cove re d .

The fre e d om of movement afforded to

Shuttle astronauts on EVAs is due to the Pri m a ry

L i fe - Su p p o rt System (PLSS) ca r ried on their

b a ck s . The PLSS, an advanced ve r s i on of the

Ap o llo sys t e m , p rovides life support , voice commu n i ca t i on s , and biom e d i cal telemetry for EVA s

lasting as long as seven hours. Within its dimens i ons of 80 by 58.4 by 17.5 centimeters, the PLSS

c ontains five major groups of com p onents for life

s u p p o rt . Those are the ox y g e n - ve n t i l a t i n g, c ond e n s a t e, fe e d w a t e r, liquid tra n s p o rt , and pri m a ry

oxygen circ u i t s .

2 6 • Suited for Spacewalking An Activity Guide for Technology Education, Mathematics, and Science, EG- 1 9 9 8 - 0 3 - 1 1 2 - H Q
The oxygen-ventilating circuit is a closed-loop

system. Oxygen is supplied to the system from the

primary oxygen circuit or from a secondary oxygen

pack that is added to the bottom of the PLSS for

emergency use. The circulating oxygen enters the

suit through a manifold built into the Hard Upper

Torso. Ducting carries the oxygen to the back of the

space helmet,where it is directed over the head and

then downward along the inside of the helmet

front. Before passing into the helmet, the oxygen

warms sufficiently to prevent fogging of the visor.

As the oxygen leaves the helmet and travels into the

rest of the suit, it picks up carbon dioxide and

h u m i d i ty from the crew member’s re s p i ra t i on .

More humidity from perspiration, some heat from

physical activity, and trace contaminants are also

picked up by the oxygen as it is drawn into the

ducting built into the Liquid Cooling-andVentilation Garment. A centrifugal fan, running at

nearly 20,000 rpm, draws the contaminated oxygen

back into the PLSS at a rate of about 0.17 cubic

meters per minute, where it passes through the

Contaminant Control Cartridge.

Carbon dioxide and trace contaminants are filtered out by the lithium hydroxide and activated

charcoal layers of the cartridge.The gas stream then

travels through a heat exchanger and sublimator for

removal of the humidity. The heat exchanger and

sublimator also chill water that runs through the

tubing in the Liquid Cooling and Ve n t i l a t i on

Garment (LCGV).The humidity in the gas stream

condenses out in the heat exchanger and sublimaSuited for Spacewalking An Activity Guide for Technology Education, Mathematics, and Science, EG-1998-03-112-HQ • 2 7
tor. The relatively dry gas (now cooled to approximately 13 degrees Celsius) is directed through a

ca rb on dioxide sensor before it is re c i rc u l a t e d

through the suit. Oxygen is added from a supply

and regulation system in the PLSS as needed. In

the event of the failure of the suit fan, a purge valve

in the suit can be opened. It initiates an open loop

purge mode in which oxygen is delivered from both

the primary and secondary oxygen pack. In this

mode, moisture and the carbon dioxide-rich gas are

dumped outside the suit just before they reach the

Contaminant Control Cartridge.

One of the by-products of the ox y g e n - ve n t i l a ting circuit is moisture . The water produced by perspira t i on and breathing is withdrawn from the ox y g e n

s u p p ly by being condensed in the sublimator and is

ca r ried by the condensate circ u i t . (The small amount

of oxygen that is also ca r ried by the condensate circ u i t

is re m oved by a gas separator and re t u rned to the ox yg e n - ventilating system.) The water is then sent to the

w a t e r - s t o rage tanks of the feedwater circuit and

added to their supply for eventual use in the sublimat o r. In this manner, the PLSS is able to maintain suit

cooling for a longer period than would be possible

with just the tank’s original water supply.

The function of the feedwater and the liquid

transport circuits is to cool the astronaut. Using the

pressure of oxygen from the primary oxygen circuit,

the feedwater circuit moves water from the storage

tanks (three tanks holding a total of 4.57 kilograms

of water) to the space between the inner surfaces of

two steel plates in the heat exchanger and sublimator. The outer side of one of the plates is exposed

directly to the vacuum of space.That plate is porous

and, as water evaporates through the pores, the

temperature of the plate drops below the freezing

point of water. Water still remaining on the inside

of the porous plate freezes, sealing off the pores.

Flow in the feedwater circuit to the heat exchanger

and sublimator then stops.

2 8 • Suited for Spacewalking An Activity Guide for Technology Education, Mathematics, and Science, EG- 1 9 9 8 - 0 3 - 1 1 2 - H Q

Astronaut Joe Tanner works on the Hubble Space Telescope during the STS-82 mission.The curvature ofEarth and the Sun are over his left shoulder.
On the opposite side of the other steel plate is a

s e c ond chamber through which water from the liquid tra n s p o rt circuit passes. The liquid tra n s p o rt circuit is a closed-loop system that is connected to the

plastic tubing of the LC VG . Water in this circ u i t ,

d ri ven by a pump, a b s o rbs body heat. As the heated

water passes to the heat exchanger and sublimator,

heat is tra n s fe r red through the aluminum wall to the

chamber with the porous wall .The ice formed in the

p o res of that wall is sublimated by the heat dire c t ly

into gas, p e rmitting it to tra vel through the pore s

into space. In this manner, water in the tra n s p o rt

c i rcuit is cooled and re t u rned to the LC VG . T h e

cooling rate of the sublimator is determined by the

w o rkload of the astron a u t . With a greater work l o a d ,

m o re heat is released into the water loop, causing ice

to be sublimated more ra p i dly and more heat to be

eliminated by the sys t e m .

The last group of components in the Primary

Life-Support System is the primary oxygen circuit.

Its two tanks contain a total of 0.54 kilograms of

oxygen at a pressure of 5,860.5 kilopascals, enough

for a normal seven-hour EVA. The oxygen of this

circuit is used for suit pressurization and breathing.

Two regulators in the circuit step the pressure down

to usable levels of 103.4 kilopascals and 29.6 kilop a s ca l s . Oxygen coming from the 103.4-kilopascal regulator pre s s u ri zes the water tanks, and ox ygen from the 29.6-kilopascal regulator goes to the

ventilating circ u i t .

To insure the safe ty of astronauts on EVA s , a

Se c on d a ry Oxygen Pa ck (SOP) is added to the bott om of the PLSS. The two small tanks in this sys t e m

c ontain 1.2 kilograms of oxygen at a pre s s u re of

41,368.5 kilopasca l s . The Se c on d a ry Oxygen Pa ck

can be used in an open-loop mode by activating a

purge valve or as a backup supply should the pri m a ry

s ystem fall to 23.79 kilopasca l s . The supply autom a ti ca lly comes on line whenever the oxygen pre s s u re

inside the suit drops to less than 23.79 kilopasca l s .

If the Displays and Control Module (DCM)

purge valve (discussed below) is opened, used-oxygen contaminants and collected moisture dump

directly out of the suit into space.Because oxygen is

not conser ved and recycled in this mode, the large

quantity of oxygen contained in the SOP is consumed in only 30 minutes.This half-hour still gives

the crew member enough time to return to the

o rb i t e r’s airl o ck . If ca rb on dioxide con t rol is

required, the helmet purge valve may be opened

instead of the DCM purge valve. That valve has a

lower flow rate than the DCM valve.

Displays and Control Module 

The PLSS is mounted directly on the back of

the Hard Upper Torso, and the controls to run it are

mounted on the front. A small, irregularly-shaped

box, the Displays and Control Module (DCM),

houses a variety of switches, valves, and displays.

Along the DCM top are four switches for power,

feedwater, communications mode selection, and

caution and warning. A suit-pressure purge valve

projects from the top at the left. It is used for

depressurizing the suit at the end of an EVA and

can be used in an emergency to remove heat and

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3 0 • Suited for Spacewalking An Activity Guide for Technology Education, Mathematics, and Science, EG- 1 9 9 8 - 0 3 - 1 1 2 - H Q

humidity when oxygen is flowing from both the

primary and secondary oxygen systems. Near the

front on the top is an alpha-numeric display. A

microprocessor inside the PLSS permits astronauts

to monitor the condition of the various suit circuits

by reading the data on the display.

Stepped down from the top of the DCM, on a

small platform to the astronaut’s right, is a ventilation-fan switch and a push-to-talk switch. The

a s t ronaut has the option of having the radio 

channel open at all times or only when needed.

On a second platform, to the left, is an illuminated mechanical-suit pressure gauge. At the bottom, on the front of the DCM, are additional controls for communications volume, display lighting

intensity, temperature control, and a four position

selector for controlling suit pressure in different

EVA operating modes.
Suited for Spacewalking An Activity Guide for Technology Education, Mathematics, and Science, EG-1998-03-112-HQ • 3 1

One of the great advantages of working in

space is that objects,including the astronauts themselves, have no apparent weight. Regardless of the

weight of an object on Earth, a single crew member

can move and position that object in orbit with ease

provided the crew member has a stable platform

from which to work.

The physics of working in space is the same as

that of working on Earth. All people and things

c ontain matter and con s e q u e n t ly have mass.

Because of that mass, they resist any change in

motion. Physicists refer to that resistance as inertia.

The greater the mass, the greater the inertia.

Like on Eart h , to change the motion of

objects in space re q u i res an applica t i on of forc e .

H ow mu ch the object moves is explained in part

by Sir Isaac Newt on's T h i rd Law of Motion . T h e

law states that a force causing an object to move

one way is met with an equal and opposite force in

the other dire c t i on . The law is more familiarly

stated as, “For eve ry action there is an opposite and

equal re a c t i on . ” The consequence of this law in

space is import a n t . A simple Earth task, s u ch as

t u rning a nut with a wre n ch , can become quite difficult in space because the astronaut—and not the

n u t — m ay turn .

Ap p l i ca t i on of force on Earth is easy beca u s e

we plant our feet firm ly on the gro u n d . We ca n

l i ft heavy objects upw a rd because the equal and

opposite force is directed dow nw a rd through our

legs and feet to Earth itself. E a rth's inertia is so

g reat that its re s p onse to the dow nw a rd force is

i n f i n i t e s i m a l . In space, on the other hand, a s t ronauts do not have the advantage of having a planet to stand on to absorb the equal and opposite

f o rce during work activities. As explained in the

T h i rd Law of Motion , pushing on an object ca u ses the object and the crew member to float away

in opposite dire c t i on s . The rates at which the

c rew member and the object float away from each

other is determined by their re s p e c t i ve masses.

For example, a massive satellite will move away

mu ch more slow ly than the less massive astron a u t

pushing on it. To gain advantage over objects, t h e

spacesuited crew member must be bra c e d ,

t h rough foot re s t ra i n t s , by a stable platform , s u ch

as a massive and active ly stabilized Shuttle orb i t e r

or Intern a t i onal Space St a t i on .

EVA

As Apollo spacesuits were being developed for

walking on the surface of the Moon,a special set of

tools was designed to assist astronauts in their sample collecting task. The Apollo suits were stiff, and

bending at the waist was difficult and awkward.

Working In Space
The problem of picking up rocks and soil samples

was solved by creating long-handled sampling tools

such as scoops and rakes. Because bulky spacesuit

gloves made grasping difficult, tool handles were

made thicker than normal.

Today's spacewalkers have an extensive collection of EVA tools to employ during Shuttle and

International Space Station missions. Several criteria are used in creating useful tools for space flight.

Tools have to be easily gripped by astronauts wearing heavy gloves. The tools have to be safe to use

and reliable under temperatures that can vary by

hundreds of degrees. Tools also need some sort of

attachment system so that if an astronaut should

"drop" them,the tools will not float away. Colliding

with a socket wrench left in orbit by some earlier

space mission could be disastrous.

In the planning phase of each mission,tools are

selected on the basis of the jobs that must be done.

Specialized tools are often created when no existing

tool will do the job. Many of the tools found in a

traditional tool box on Earth are used in space as

well. The tools are modified to make them easier

and safer to use in space. For example, the handles

of tools are often enlarged so they will take less

energy to hold. A spacesuit glove is similar to a

thick leather welder's glove in bulk.Because the suit

glove is pressurized, the astronaut's fingers extend

out when at rest. Closing the fingers around a tool

handle takes a continuous application of force.

Quite simpl y, small-handled tools take more force

to hold than do large-handled tools.

To keep control of tools, each tool has some

sort of tether or locking system. A socket wrench

has a key that has to be inserted into a holder before

a socket can be installed at the end of the wrench.

Once the key is removed, the socket is then locked

onto the wrench and cannot be removed without

use of the key again.A short tether and clip enables

the astronaut to hang on to the wrench in case it is

d ro p p e d . T h e re is even a tether on the key.

Rechargeable power tools for driving bolts are also

used by spacewalkers.

3 2 • Suited for Spacewalking An Activity Guide for Technology Education, Mathematics, and Science, EG- 1 9 9 8 - 0 3 - 1 1 2 - H Q

STS-82 Astronaut Steven L.Smith holds a power ratchet tool as he prepares to replace some ofthe instruments on the Hubble Space Telescope.
Suited for Spacewalking An Activity Guide for Technology Education, Mathematics, and Science, EG-1998-03-112-HQ • 3 3

Safety

Tether Probe

Mechanical

Fingers

Bolt Puller

Hammer

Vise Grips

Small

Cutter

Adjustable Wrench

Allen Wrench

The tools shown here are representative samples ofthe tools available to spacewalkers.Many EVA tools are standard Earth tools that have been modified for space

use. Loops,to attach tethers,are added to prevent loss in orbit. For some tools,such as the adjustable wrench and probe, the handle has been enlarged to make grasping with a spacesuit glove less tiring .

EVA Tools
Astronaut Maneuvering Units

Du ring the first Am e ri can EVA , E d w a rd Wh i t e

e x p e rimented with a personal pro p u l s i on dev i c e, t h e

Hand-Held Maneuve ring Unit (HHMU). T h e

HHMU tested by White was a three-jet maneuve ri n g

g u n . Two jets were located at the ends of rods and

aimed back so that firing them pulled White forw a rd .

A third jet was aimed forw a rd to provide a bra k i n g

f o rc e . By holding the gun near his center of mass and

aiming it in the dire c t i on in which he wanted to tra ve l ,he was able to propel himself forw a rd . Stopping that

m ovement re q u i red firing the center jet. The pro p u ls i ve force of the HHMU was produced by re l e a s i n g

c om p ressed oxygen from two small built-in tanks.

Although the HHMU worked as intended, i t

had two disadvantages. To produce the desire d

m o t i on , it had to be held as close to the astron a u t ' s

center of mass as possible. D e t e rmining the center

p o s i t i on was difficult because of the bulky spacesuit

White wore and was a matter of guesswork and

e x p e ri e n c e . Fu rt h e rm o re, p recise motions to posit i on an astronaut pro p e rly during an activity such as

s e rvicing a satellite were difficult to ach i eve and

maintain and proved phys i ca lly exhausting.

On the Gemini 9 mission, a backpack maneuvering unit was carried. However, problems with

the unit prevented Gene Cernan from testing it.

Fo ll owing the Gemini pro g ra m , the next space

e x p e riments that tested maneuve ring units for EVA s

t o ok place during the second and third manned

Sk ylab mission s . The device was tested on ly inside

the spacecra ft , but the experiment con f i rmed that a

m a n e u ve ring device of that design was both fe a s i b l e

and desirable for future EVA use. Fi ve of the six

a s t ronauts who flew in those two missions accumulated a total of 14 hours testing the advanced dev i c e,

ca lled the AMU, or Astronaut Maneuve ring Unit.

The AMU was shaped like a large ve r s i on of a

h i k e r’s back p a ck . Built into the frame was a re p l a c eable tank of com p ressed nitrogen gas. C on t rols for

the unit were placed at the ends of “a rm re s t s . ” To

m ove, the astronaut worked ro t a t i onal and tra n s l at i onal hand con t ro l s . Pro p u l s i ve jets of nitrogen gas

w e re released from various nozzles spaced aro u n d

the unit. The 14 nozzles were arranged to aim topb o t t om , f ron t - b a ck , and ri g h t - l e ft to produce six

d e g rees of fre e d om in move m e n t . The AMU could

m ove forw a rd and back , up and dow n , and side to

s i d e, and could ro ll , p i t ch , and yaw. With the 11

a d d i t i onal nozzles, p recise positioning with the

AMU was far simpler than with the HHMU of the

Gemini pro g ra m . The astronaut was surrounded by

the unit, taking the guesswork out of determ i n i n g

center of mass and making con t rol mu ch more accura t e . The astronaut could move cl o s e ly along the

s u rface of a curved or irre g u l a rly-shaped object

without making contact with it.

The AMU led to the MMU or manned

m a n e u ve ring unit for use during early Sp a c e

Shuttle flights. It was designed to operate in the

microgravity environment of outer space and under

the temperature extremes found there. The MMU

was operated by a single space-suited astronaut.

The unit featured redundancy to protect against

failure of individual systems. It was designed to fit

over the life - s u p p o rt system back p a ck of the

Shuttle EMU.

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Bruce McCandless II pilots the MMU in space for its first flight.
The MMU was approximately 127 centimeters

high,83 centimeters wide, and 69 centimeters deep.

When carried into space by the Shuttle, it was

stowed in a support station attached to the wall of

the payload bay near the airlock hatch.Two MMUs

were carried on a mission with the second unit

mounted across from the first on the opposite payload bay wall. The MMU controller arms were

folded for storage, but when an astronaut backed

into the unit and snapped the life-support system

into place, the arms were unfolded. Fully extended,

the arms increased the depth of the MMU to 122

centimeters. To adapt to astronauts with different

arm lengths, controller arms could be adjusted over

a range of approx i m a t e ly 13 centimeters. T h e

MMU was small enough to be maneuvered with

ease around and within complex structures. With a

full propellant load, its mass was 148 kilograms.

Gaseous nitrogen was used as the propellant

for the MMU. Two aluminum tanks with Kevlar®

filament overwrappings contained 5.9 kilograms of

nitrogen each at a pressure of 20.68 kilopascals,

enough propellant for a six-hour EVA, depending

on the amount of maneuvering done. In normal

operation,each tank fed one system of thrusters. At

the direction of the astronaut, through manual control or through an automatic attitude-hold system,

propellant gas moved through feed lines to varying

combinations of 24 nozzles arranged in clusters of

three each on the eight corners of the MMU. The

nozzles were aimed along three axes perpendicular

to each other and permit six degrees of freedom of

movement. To operate the propulsion system, the

astronaut used his or her fingertips to manipulate

hand controllers at the ends of the MMU’s two

arms.The right-hand controller produced rotational acceleration for roll,pitch,and yaw. The left controller produced acceleration without rotation for

m oving forw a rd - b a ck , u p - d ow n , and left - ri g h t .

Coordination of the two controllers produced intricate movements in the unit. Once a desired orient a t i on had been ach i eve d , the astronaut could

engage an automatic attitude-hold function that

maintained the inertial attitude of the unit in flight.

This freed both hands for work.

The MMU was used on three Shuttle missions

in the mid 1980s. It was first tested by Bruce

McCandless and Robert Stewart on the 1984 STS

Suited for Spacewalking An Activity Guide for Technology Education, Mathematics, and Science, EG-1998-03-112-HQ • 3 5

SAFER Propulsion Module

Stowed

Deployed

Hand Controller
3 6 • Suited for Spacewalking An Activity Guide for Technology Education, Mathematics, and Science, EG- 1 9 9 8 - 0 3 - 1 1 2 - H Q

41-B mission. Taking turns, the two astronauts

flew the MMU out from the orbiter's payload bay

to a distance of about 100 meters and tested complex maneuvers. On STS-41C, the next Shuttle

mission, James Van Hoften and George Nelson

used the MMU to capture the Solar Maximum

mission satellite and bring it into the orbiter's payload bay for repairs and servicing. Their work

increased the life span of the satellite. The final

MMU mission was STS-51A that flew in

November of 1984.The propulsion unit was used to

retrieve two communication satellites that did not

reach their proper orbit because of faulty propulsion

modules. Joseph Allen and Dale Gardner captured

the two satellites and brought them into the orbiter

payload bay for stowage and return to Earth.

M o re recent experiments with astron a u t

m a n e u ve ring units took place on the 1994 STS-64

m i s s i on . A new dev i c e, ca lled the Simplified Aid

for Extra vehicular activity Rescue (SAFER) was

f l own by Mark C. Lee and Carl J. Meade a few

meters away from their orb i t e r. S A F ER is a smaller unit than the MMU and is designed as a selfrescue device for use on the Intern a t i onal Sp a c e

St a t i on . Although unlikely, an astronaut could

b e c ome separated from the station during an EVA

and a Shuttle not be available to re t ri eve the crew

m e m b e r. In that eve n t , the crew member would use

the pro p u l s i ve power of SAFER to re t u rn to the

s t a t i on stru c t u re .

SAFER fits over the portable life support

system of the Shuttle EMU. A control module 

consisting of a joystick and display is stowed in the

bottom of SAFER. During operation, the control

module is moved to the suit's front for easy access.

With the controls the astronaut can expel nitrogen

gas through 24 nozzles that are fixed in different

orientations around the device. An autopilot system

is available to keep the astronaut at the same orientation for a limited period of time. SAFER features

the same maneuverability as the MMU but because

its nitrogen tank only holds 1.4 kilograms of nitrogen gas, the total velocity change possible with the

unit is 3.05 meters per second.

Mark C.Lee test flies the Simplified Aid for Extravehicular activity Rescue

(SAFER) device during the STS-64 mission.
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In recent ye a r s , NASA has increased the freq u e n cy of extra vehicular activity to pre p a re for the

a s s e m b ly of the Intern a t i onal Space St a t i on beginning in the late 1990s. Two recent extra o rd i n a ry

Shuttle missions have demon s t rated the potential

for EVA on the Space St a t i on . These were the 

STS-61 and STS-82 missions in 1993 and 1997 in

w h i ch astronauts conducted multiple spacewalks to

s e rvice the Hubble Space Te l e s c o p e . Du ring each

f l i g h t , c rew members donned their spacesuits and

c onducted EVAs in which they replaced instru m e n t s

and installed new solar panels.Their servicing activities re q u i red extreme pre c i s i on and dexteri ty duri n g

EVAs lasting more than seven hours.

Similar efforts will be needed for the assembly

of the International Space Station. During the

nearly 40 American and Russian space flights to the

station, astronauts and cosmonauts will log over

1,200 hours of EVAs.More hours of spacewalks are

expected to be conducted during just the years 1999

and 2000 than were conducted during all previous

US space flights.

Sp a c ewalkers will assist in the assembly of the

Space St a t i on by making all the con n e c t i ons that

re q u i re greater dexteri ty than can be accom p l i s h e d

with station ro b o t s . These opera t i ons include joining

e l e c t ri cal cables and fluid tra n s fer lines and install i n g

and deploying com mu n i ca t i on antennas. To do this,

EVAs on the International Space Station

STS-82 (1997) astro n auts Mark C. Lee (top) and Steven L. Smith (bottom)

repair a worn area in the insulation of the Hu b ble Space Tel e s c o p e. D e ta i l e d

w o rk like this will be a frequent occurrence during the assembly and opertion of

the International Space Sta t i o n .
3 8 • Suited for Spacewalking An Activity Guide for Technology Education, Mathematics, and Science, EG- 1 9 9 8 - 0 3 - 1 1 2 - H Q

s p a c ewalkers will have to re m ove locking bolts that

s e c u red com p onents during launch to orb i t .

As the Space St a t i on ev o lve s , a s t ronauts will

m ove com p on e n t s , s u ch as antennas, to the most

advantageous loca t i on s . For example, a com mu n ica t i ons antenna may become blocked when addit i onal station modules are joined to the stru c t u re .

Sp a c ewalkers will have to tra verse the outside of

the modules and re p o s i t i on the antenna where it

w i ll be unblocked by modules, solar panels, a n d

other stru c t u re s .

Still other Space Station EVA assembly tasks

include removing of locking bolts for solar panels

and radiators, driving bolts that hold the truss

assembly to the Space Station, attaching grapple

fixtures to objects that have to be moved by the

Space Station's robot arms, mounting tool kits,

adding batteries, and reconfiguring valves for fluid

transfer. Later, during the operational phase of the

I n t e rn a t i onal Space St a t i on , s p a c ewalkers will

replace orbital replacement units (ORUs). These

are modular devices, such as the scientific instruments on the Hubble Space Telescope, that are

designed to be removed periodically and replaced

with improved or more advanced equipm e n t .

O p e ra t i onal spacewalks will also take ca re of

mounting external payloads that are brought up to

the Space Station on the Space Shuttle.

STS-76 astronaut Michael R. Clifford works with a restraint bar on the Docking Module ofthe Russian MIR space station.Similar docking modules (Pressurized

Mating Adaptor) will be used on the International Space Station.
Suited for Spacewalking An Activity Guide for Technology Education, Mathematics, and Science, EG-1998-03-112-HQ • 3 9

The current Extra vehicular Mobility Unit

(EMU) and all its associated EVA systems are the

result of many years of research and development.

They now comprise a powerful tool for orbital

operations, but they are not end-of-the-line equipment. Many improvements are possible; the spacesuit of the future may look dramatically different

from the Space Shuttle EMU.

Advanced versions of the EMU are being studied, including spacesuits that operate at higher

pressures than the current EMU. The advantage of

higher operating pressures is that virtually no time

will be lost to prebreathing in preparation for EVA.

To build an opera t i onal high-pre s s u re suit

requires improved joint technology and integration

of those joints into the suit.Under consideration are

fabric and metal suits and suits with a hard external

shell. Most of the technology needed for these suits

has already been tested. One of the biggest challenges is to make a highly mobile glove. At higher

operating pressures, fingers of older-style spacesuit

gloves become so increasingly stiff that finger dexterity is severely reduced. Research to address this

problem has led to the development of high-pressure gloves made with metal bands for knuckle and

palm joints. These gloves show potential for use

with future suits as well as with current suits, but

there is still more work to be done. One line of

Future Space Suits

The Mark III Hard Suit is modeled by a spacesuit engineer.
research has explored incorporating robotic aids

into the glove such as motor and cable systems to

provide grasping force at higher pressures. So far,

such systems have not been successful because of

the extra bulk added to the hands and arms of the

suit and because of the "what if" problem of a system failing while the hand is clamped onto an

object. That could make it very difficult to release

the object.

Another improvement in suit design will permit servicing and resizing suits in orb i t . T h i s

improvement has already been tested on the STS82 mission to service the Hubble Space Telescope.

The original design of the Space Shuttle EMU

required the removal or the addition of sizing

inserts to lengthen or shorten legs and arms. This

was a lengthy process because it involved lacing

pieces together. Quick disconnect sizing inserts

have been designed that greatly speed up and simplify the process.The new system involves threaded

q u i ck discon n e c t s , aluminum sizing ri n g s , a n d

adjustable restraint lines.The capability of servicing

and resizing suits in space is vital for operations on

the International Space Station. There, crew members will remain in space for months at a time, and

EVAs will be routine events. With this and other

improvements in design, spacesuits will be able to

be used 25 times on the International Space Station

over a period of 180 days before they have to be

returned to Earth for major reservicing.

Another suit improvement is an electronic version of the checklist worn on the arm. The new

system,similar to a pocket electronic organizer, will

enable the spacewalker to run through complex

sequences at the touch of a button. The checklist

can be easily reprogrammed for new tasks. It may

also have the capability of displaying television pictures from external cameras.

4 0 • Suited for Spacewalking An Activity Guide for Technology Education, Mathematics, and Science, EG- 1 9 9 8 - 0 3 - 1 1 2 - H Q

A prototype ofa next-generation spacesuit is tested.

Spacesuit technicians test the mobility ofa proposed hybrid suit design.
Other Worlds

For the most part, the design of a spacesuit is

based on the environment in which it operates.

Space Shuttle spacesuits for use in Earth orbit are

designed to operate in a vacuum and microgravity.

A spacesuit for use on the surface of the Moon or

Mars will require a different design. On the Moon,

a Space Shuttle style spacesuit would weigh about

19 kilograms. The suit will operate in an environment in which there is an up and a down direction.

Circulatory pumps in the suit will face increased

loads. Temperature extremes on the Moon will be

about the same as in orbit about Earth when in

direct sunlight and in shade. However, when the

astronaut walks on the Moon,heat will be conduct -

ed into or out of the suit via the feet. On Mars, a

Space Shuttle style spacesuit would weigh about 

43 kilogra m s , exhausting the astronaut who 

has to wear it for long periods of exploration.

Consequently, lighter EMU structures will be needed to lessen the load a future Martian explorer will

carry. In addition, the thin Martian atmosphere

may provide too much pressure for a cooling sublimator to work. Some other cooling strategy will

have to be devised. Still another concern is to provide protection from dust that is carried by Martian

winds and will be kicked up by the explorers. On

the Moon,lunar sediment is very angular and abrasive but there is no atmosphere to stir it up. Until

samples of the Martian sediment are returned to

Earth,we won't know how abrasive it will be.These

and other properties of the Moon and Martian

environment provide interesting and exciting challenges to spacesuit designers and builders.

EVA

St a rting with Edward White II’s spacewalk in

1 9 6 5 , Am e ri can astronauts have logged many hund reds of hours of extra vehicular activity in space.

M i s s i on planners corre c t ly foresaw the role EVA

would play in future space mission s . The early

Gemini experience was pri m a ri ly experi m e n t a l .

Du ring the Ap o llo and Sk ylab pro g ra m s , EVA was

c ri t i cal to success. With the Space Shuttle and the

I n t e rn a t i onal Space St a t i on , it is even more cri t i ca l .

By donning the EM U, an astronaut becomes a

s m a ll , s h o rt - t e rm spacecra ft . Space-suited crew

members can manipulate payl o a d s , make adjustm e n t s , repair broken part s , join pieces together,

Suited for Spacewalking An Activity Guide for Technology Education, Mathematics, and Science, EG-1998-03-112-HQ • 4 1

A future Martian explorer takes rock samples dangling offthe escarpment of

the Olympus Mons volcano. Pat Rawlings,SAIC.
4 2 • Suited for Spacewalking An Activity Guide for Technology Education, Mathematics, and Science, EG- 1 9 9 8 - 0 3 - 1 1 2 - H Q

and handle a host of other activities. Most import a n t , t h ey bring with them the human ability to

cope with unexpected or unusual situations that

occur in the hard and unforgiving env i ronment of

outer space.

Future spacewalkers will roam the surface ofthe Moon and Mars.This picture, painted by artist Pat Rawlings ofSAIC,shows the first humans to explore the surface ofMars.The explorers, wearing spacesuits specially-designed for the Martian environment,are scouring the surface looking for clues to the planet’s history and

evidence for signs oflife.
Suited for Spacewalking An Activity Guide for Technology Education, Mathematics, and Science, EG-1998-03-112-HQ • 4 3

Activities–Designing Spacesuits for Mars

Technology Education, Science, and Mathematics
Introduction:

The steps spacesuit engineers and technicians followed in achieving a goal of creating reliable spacesuit systems for exploration of the surface of the

Moon and for construction and maintenance work

in Earth orbit were the same as those used in nearly every technological endeavor:

Challenge

Design and construct a protective garment that will

permit humans to venture safely into outer space

and perform work.

Research

Investigate the environment in which the garment

will be worn and determine what protective measures must be employed.

Management

Organize the effort into teams that design suit subs ystems and investigate and select appro p ri a t e

materials and technologies.

Fabricate Prototypes

Construct and assemble suit subsystems into the

completed garment.

Evaluate 

Test the garment in a simulated space environment

and make modifications where needed.

Manufacture 

Construct operational spacesuits.

Ongoing Evaluation 

Continue refining spacesuit subsystems to improve

efficiency, reliability, versatility, and safety while

lowering costs.

The pages that follow outline a multifaceted technology education activity on spacesuits. This activity, designed for an entire class to work on as a

team, combines skills and content from science,

mathematics, and technology. The challenge is to

design and build a full-scale wearable model spacesuit to be used to explore the surface of Mars. Since

no human expeditions to Mars are planned for

many years, actual Martian spacesuits have not yet

been built and there are no "right" answers.

Consequently, this activity permits students to participate in "leading edge" research.

The overview of the activity is contained in a

Design Brief format. It begins with a title and a

context statement (introduction) and is followed by

a challenge to create a Martian spacesuit. This is

followed by information on materials, equipment,

procedures, and evaluation. The success of the

activity depends upon how well the students organize their work and communicate with each other.

A computer with project software can be used to

monitor the progress of the project or a flow chart

can be constructed on a chalk or bulletin board. As

an added aid to communication, Interface Control

Documents (ICD) are created as systems are

designed.(Reproducible master on page 49. Sample

4 4 • Suited for Spacewalking An Activity Guide for Technology Education, Mathematics, and Science, EG- 1 9 9 8 - 0 3 - 1 1 2 - H Q

Technology Education is a multi-disciplinary subject combining mathematics,

science, and technology.
Suited for Spacewalking An Activity Guide for Technology Education, Mathematics, and Science, EG-1998-03-112-HQ • 4 5

document on page 50.) These documents are completed by the teams. Critical details about systems,

such as size, shape, and function, are recorded on

the form. The form has a grid where diagrams can

be made. ICD forms are then placed in a notebook

and made available to all teams as a coordination

tool. An ICD master is provided.

If desired, the project can be divided among several

classes (or even several schools) which will each

have to work together. This is the way major NASA

projects are divided between contractors and subcontractors located across the country.

To support the activity, a coll e c t i on of Te a cher Te ch

B ri e fs (TTB) are incl u d e d . These bri e fs prov i d e

s u g g e s t i ons for your use when guiding students in

a c c omplishing their tasks. For example, if student

teams con clude that high-speed part i cles (microm et e o roids) are a problem in the Martian env i ron m e n t ,

plans are provided for a device that measures impact

damage to materi a l s .TTBs are not intended as "blue

p rints" for students to use. Ra t h e r, t h ey prov i d e

i n f o rm a t i on on one of many ways in which the task

can be accom p l i s h e d . Students will build an impact

test stand of their own design.TTBs aid you in facilitating the students' ideas. Fo ll owing the TTBs is a

s e c t i on on spacesuit testing apparatus used at the

NASA Joh n s on Space Center. The apparatus are

" one of a kind" devices created by foll owing the

same design process students will use.

Exploration Briefs (EBs) are suggestions for activities that can be used to help students understand

the nature of the environment for which they are

designing a spacesuit. They provide background

information and instructions for simple demonstrations and experiments that may be tried. A "bank"

of additional ideas follow the EBs.

The guide concludes with appendices that list

re s o u rc e s , s u ch as NASA publica t i ons and Intern e t

web sites,w h e re students can obtain more inform a t i on

to help them in their re s e a rch and deve l o pment work .
Design Brief

Suited for Spacewalking An Activity Guide for Technology Education, Mathematics, and Science, EG-1998-03-112-HQ • 4 7

C o n t ex t :

Spacesuits are one of the important enabling technologies that have permitted humans to explore outer

s p a c e .To surv i ve the hostile env i ron m e n t , humans had to be cove red with a pro t e c t i ve shell as they exited their spacecra ft . This shell contained a part of Earth's surface env i ronment while remaining flexible

and impervious to the unique haza rd s , s u ch as high-speed part i cle impacts, e n c o u n t e red there .T h e s e

re q u i rements meant that engineers and technicians had to spend long hours investigating and selecting

a p p ro p riate materi a l s , finding ways of fabri cating and joining suit parts together, and providing opera ting pre s s u re, p ow e r, and com mu n i ca t i ons while assembling a garment that was tough but flexible. T h e

task was ach i eved with such great success that astronauts and cosmonauts have safe ly conducted thousands of hours of extra vehicular activity.

C h a ll e n g e :

Design and build a pro t e c t i ve garment that will permit future space tra velers to explore the surface of

M a r s . The garment must protect the person inside from the haza rds of the Martian env i ronment while

remaining com f o rtable to wear. E xc u r s i ons on the surface will nom i n a lly last 8 hours, but the garm e n t

w i ll have to function as long as 10 hours in emergency situation s . The garment must be flexible enough

to enable the wearer to walk up to 10 kilom e t e r s ,c o llect geologic samples, and operate a vari e ty of tools

and experimental appara t u s . Fu rt h e rm o re, the garment's design must be rugged enough to perm i t

repeated use and be able to be serviced simply and quick ly. A l ong with the garm e n t , design a coll e c t i on

of geologic sampling tools,s u ch as ro ck hammers, and a general set of tools for assembly and repair activi t i e s . These tools should be easy to use while wearing the pro t e c t i ve garm e n t , be safe and ru g g e d , a n d

i n t e rface with a general purpose tool ca r rier that must also be designed.

Pro c e d u r e s :

Select subcontractor teams to design and construct each of the garment's components, such as the

helmet or gloves. Teams will coordinate their work with each other as materials for and sizes of the

components are selected.

M a t e ri a l s :

Use whatever materials you find to con s t ruct the garment's com p on e n t s .Test these materials to ensure

t h ey will surv i ve the Martian env i ron m e n t . Existing tools can be modified for use on Mars.

E v a l u a ti o n :

C onduct periodic team ev a l u a t i ons of the pro g ress of the garment and tool design pro c e s s . When all

c om p onents are com p l e t e d ,i n t e g rate them for a full test in a simulated Martian env i ron m e n t .E v a l u a t e

the garment and tools on the basis of the cri t e ria presented in the context section .
Interface Control Document

System Name: Team Members

Project No.

Date: Rev. No.

Page Of

Briefly explain how this system functions.
Suited for Spacewalking An Activity Guide for Technology Education, Mathematics, and Science, EG-1998-03-112-HQ • 4 9

I n t e rface Con t rol Documents are a com mu n i ca t i on tool that helps the various Martian Su rface Explora t i on

Suit design teams to coordinate with each other. This sample shows a design for a space helmet. The team

w o rking on the upper torso will learn from this document how large the con n e c t i on with the helmet has to be.

SCALE: 1:5 MASS: 5 kg POWER REQUIREMENTS: 6 volts

SAMPLE

Neck ring - 25 cm in diameter

Helmet - 40 cm in diameter

Sun Visor

Lights (3)

Window

Interface Control Document

System Name: Space Helmet Team Members

Project No. 8 Peter

Date: Nov. 22, 1997 Rev. No. 4 Kiesha

Page 1 Of 1
Suited for Spacewalking An Activity Guide for Technology Education, Mathematics, and Science, EG-1998-03-112-HQ • 5 1

Context

The different materials used in constructing the

Space Shuttle EMU were chosen because they each

featured properties deemed desirable for spacewalki n g. Depending upon their intended purp o s e,

material may have to withstand tears, punctures,

temperature extremes, bending, abrasion, or any

combination of the above.

Purpose

This test stand measures materials for their resistance to tensile (stretching) forces.

Principle

Using the mech a n i cal advantage of a pull ey setup,t e nsile forces are exe rted on test samples until they bre a k .

Materials and Tools Checklist

Wooden base (6" x 1" x 4')

Threaded iron pipe (1 pc 3/4" x 2') 

(2 pcs 3/4" x 3')

Pipe elbows (2 pcs )

Pipe flanges (2 pcs )

Screws for flanges

Pulley (1 single)

Pulley block (1 double, 1 triple)

Cord for pulleys

Clamps (2 )

Metric Ruler

Pointer (stiff wire)

Hose clamps (2 pcs )

Lead weights (25 kg)

Bucket

Screwdriver

Pipe wrench

Materials to be tested

Eye Protection

Operation

Obtain diffe rent fabric samples from re m n a n t

tables at fabric stores. Also ask students to bring in

samples with which to work.Cut the material to be

tested into a rectangular strip 1 centimeter by 10

centimeters in size.The sample is held between two

clamps as shown in figure 1. Place a small number

of lead weights in the bucket to counterbalance the

weight of the clamp and pull ey assembly so that the

sample material is held upri g h t . R e c o rd the position

of the wire pointer on the ru l e r. This is the ze ro forc e

m e a s u re m e n t . G ra d u a lly add measured weights to

Teacher Tech Brief

Tensile Strength Test Strand
5 2 • Suited for Spacewalking An Activity Guide for Technology Education, Mathematics, and Science, EG- 1 9 9 8 - 0 3 - 1 1 2 - H Q

the buck e t . The mech a n i cal advantage of the pull ey

a r rangement magnifies the actual pull (tensile forc e )

on the sample five times. R e c o rd the tensile forc e

(the weight in the bucket multiplied by five) and the

p o s i t i on of the pointer. The position of the pointer

i n d i cates how mu ch the fabric stre t ches as the forc e

i n c re a s e s . Add more weight and re c o rd the data.

C ontinue this process until the sample breaks or yo u

run out of weights. C reate a gra ph to demon s t ra t e

the perf o rmance of the materi a l .

Tips

• An empty metal gallon-size paint bucket can be

used to hold the lead weights.

• Used wheel-balancing lead weights can be

obtained free or for little cost at tire stores.

• In some materials, tensile strength varies with

the direction the force is exerted. Compare cut

crosswise to the grain and on the bias.

• For very strong fabrics (e.g. Kevlar®) test a 

narrower strip or even single strands and extrapolate the results to the force a one-centimeter

wide piece could withstand.

• The test stand can be modified for other

m a t e rials tests.

• Students should wear eye pro t e c t i on when

operating the apparatus.

• Details on how to attach the clamps to the

apparatus have not been provided because of the

variety of clamping devices that could be used.

Students building the apparatus will have to

determine how this is done.

Extensions

• C ontact manufacturers of "high-tech" fabrics and

fibers for specifica t i on sheets on the pro p e rties of

their pro d u c t s . Some manufacturers may have

web sites on the Intern e t . C onduct an Intern e t

s e a rch using terms such as Kevlar® and Nom e x ® .

• Visit a sail maker's shop to learn about materials

being used for sail construction and how fabrics

are stitched together for maximum strength.

• Learn about how fabrics are manufactured and

how different properties are achieved through

fiber choice, weaving techniques, and coatings.

Check for videotapes in school video catalogs.

Pulley close-up

view
Suited for Spacewalking An Activity Guide for Technology Education, Mathematics, and Science, EG-1998-03-112-HQ • 5 3

G ra p h i c

One of the haza rds of spacewalking is the presence of

s m a ll high-speed part i cl e s . These part i cles are ca ll e d

m i c rom e t e o roids and usually are smaller than a gra i n

of sand, h a ve a mass that is on ly a fra c t i on of a gra m ,

and tra vel at speeds ranging from a few to as many as

80 kilometers per secon d . An astronaut stru ck by a

m i c rom e t e o roid could be seve re ly injure d .Fu rt h e rm o re,

the near-Earth space env i ronment has the addition a l

p roblem of space debris such as paint chips and metal

f ragments from old ro cket boosters and satell i t e s .

Being stru ck by one of these part i cles is equally dang e ro u s . As a con s e q u e n c e, spacesuits have to be cons t ructed from materials that are resistant to impacts.

Pu rpo s e

This test stand measures the resistance of sample

m a t e rials to impacts.

Pri n c i p l e

The test stand consists of a tow e r, made from pipe,

with an electromagnet near the top. A center punch

(impactor) is suspended from the magnet and dro p s

when the electri c i ty is cut off. The center punch fall s

into a test sample placed below.

Materials and Tools Checklist

Wooden base (6" x 1" x 2')

PVC plastic water pipe (3/4" x 10')

Pipe elbows (2 pcs)

Pipe flanges (1 pc)

Screws for flange

Bell wire

Large eye screw

Electronic project box

On/off switch

Pilot light

Push button switch

6 volt battery holder

Wooden block (1" x 6" x 6")

Center punch

Screw driver

Meter stick

Test materials

Tape or pins

Operation

Cut the material to be tested into a small square and

tape or pin it on the test surface block (1" x 6" x 6"

wooden block ) . A fter positioning the test materi a l ,

t u rn on the electromagnet and attach the impactor.

Teacher Tech Brief

Impact Resistance Tester
Measure the distance between the point of the electromagnet and the test material. When the impactor

and magnet stop swinging, turn off the electric current to release the impactor. As it falls, the impactor

will accelerate into the sample and make a dent or

even penetrate it. Evaluate the resistance to impacts

of various materials by comparing the damage done

to them. Use a metric ruler for measuring the diameter of the dent or hole.

Mathematics Equations

In physics, the energy of a moving object is called

kinetic energy. The amount of that energy is related

to the object’s mass and its speed. The equation

below can be used to determine the kinetic energy

of the falling center punch at the moment of its

impact on the test surface. The answer will be in

joules (unit of work equal to a force of one Newton

exerted over a distance of one meter; in English

units, a joule is approximately equal to 0.75 foot

pounds).

KE = 1/2 mv2

m = mass of impactor 

v = velocity at impact

To determine the velocity at the impact, use the

following equation:

v = gt

g = the acceleration of gravity or 9.8m/second2

t = length of time the impactor fell

To determine the length of time the impactor falls.

use the following equation:

t = 2d

g

d = the distance the impactor fell, in meters

Sample Problem

d = 2 m

Impactor mass = 50 grams 

What is KE?

v = 9.8m/s2

x 0.64s = 6.3m/s

KE = 1/2 x 0.05kg x (6.3m/s) 2 = 1.19 joules

54 • Suited for Spacewalking An Activity Guide for Technology Education, Mathematics, and Science, EG-1998-03-112-HQ Distance Impactor Falls

Electromagnet

Impactor

Test Surface Block

Tower

(Two Meters Tall)

6 Volt Power

Supply
Special Note

In this simulation of m i c ro m e te o roid impact we are

s u b s t i tuting an impactor with a large mass and low

vel o c i ty for a micro m e te o roid with a small mass and a

high vel o c i ty. The reason for this can be seen in the first

two equations on the previous page. Vel o c i ty is a 

q u ad ratic factor while mass is a linear fac t o r. B e cau s e

o f this trad e, we can ach i eve similar damage to the 

s u rf ace of a material being impac te d. Ho wever,

m i c ro m e te o roids usually vap o rize upon impac t . If t h e

s u rf ace layer is penetra te d, the gas produced disperses on

the material beneath.

Safety Precautions

1 .A ll ope rators and observers must wear eye pro t e ction during dro p s .

2 . The materials to be tested should be placed on the

test stand before the impactor is suspended fro m

the electro m a g n e t . Nothing but the material to be

tested should under the suspended impactor.

Tips

• Parts for the impactor design pictured in this

activity are available from hardware stores (pipe

parts, screws, eye screw, center punch) and

electronic parts stores (project box,switch,battery holder, pilot light, electromagnet wire).

• Make your electromagnet by wrapping electromagnet wire about 400 times around a large eye

s c rew. When the magnet is electrified the blunt

end of the impactor will be held by the magnet.

When the current is turned off, the magnet

impactor will drop straight to the target.

• Have students bring in various materials for

testing such as fabrics and plastics. Encourage

students to create composite materials by combining two or more materials together.

• Ask students to keep a test log containing data

f rom each test. E n c o u rage students to pre d i c t

the amount of damage a sample will re c e i ve during a test and com p a re that to the actual re s u l t s .

• Discuss the relative merits of the materials the

students tested. For example, a thick layer of

Suited for Spacewalking An Activity Guide for Technology Education, Mathematics, and Science, EG-1998-03-112-HQ • 5 5

6 Volts

On/Off

Switch

Arming

Light

Momentary

On Switch

Leads To

Electromagnet

Power Supply OnOff

Wiring Diagram for Power Supply Finished Power Supply
5 6 • Suited for Spacewalking An Activity Guide for Technology Education, Mathematics, and Science, EG- 1 9 9 8 - 0 3 - 1 1 2 - H Q

steel would make an excellent micrometeoroid

shield but would probably be too heavy and too

inflexible to be of use in a Martian suit.

• B e f o re running tests on impact re s i s t a n c e, u s e

E x p l o ra t i on Brief on Microm e t e o roids and

Space Debris (p. 67) with the students to

i n t roduce the topic of spacesuits and impacts.

A fter your students have selected materials for

their spacesuit, ch a llenge them to wrap a

potato in their materials and see if the materials prevent penetra t i on in the drop test.

R e fer to the potato astronaut activity for more

i n f o rm a t i on .

• A typ i cal microm e t e o roid has a mass of 1x10-5

g rams and tra vels at about eight kilometers per

s e c on d .U p on impact, a p p rox i m a t e ly three joules

of work is expended.

• A drop tower is not necessary for this test. T h e

e l e c t romagnet can be suspended from a pull ey

f rom the ceiling. The tow e r, h ow ever makes

the unit ve ry portable and eliminates any haza rds associated with attaching a pull ey to a

high ceiling.

• For younger students, begin studying the

mathematics of the device with observations

on the speed of the impactor as it falls. It will

be observed that the farther the impactor falls,

the faster it falls.

Extensions

• The impactor can be dropped from any height

when testing materi a l s . At what height should

the impactor be suspended to equal the

impact of a microm e t e o roid in space if the

m i c rom e t e o roid has a mass of 1x10-5 gra m s

and a ve l o c i ty of 8,000 meters per secon d ?

Ve l o c i ty of 16,000 meters per second? (Yo u r

answers will depend upon the mass of the

impactor you use.)

• How much kinetic energy is expended by the

micrometeoroid above? 

• Challenge the students to combine the equations on the previous page into simpler mathematical statements.

• How high should the impactor be before dropping to simulate the impact of a microm e t e o ro i d

with a mass of 1x10-5 grams and a ve l o c i ty of

eight kilometers per second? How high should

the impactor be suspended if the micrometeoroid's velocity is 16 kilometers per second?
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Background

M a ny years before Ap o llo astronauts walked on

the surface of the Moon , s ome scientists speculated that lunar dust might pose a significant haza rd .

Dust accumu l a t i ons in old craters could be quite

deep and swall ow up an unsuspecting astron a u t

that tried to cross on e . Lunar Su rveyor spacecra ft

that landed on the Moon prior to the Ap o llo exped i t i ons showed that lunar dust (ca lled re golith or

sediment) had on ly accumulated to the depth of a

few centimeters and there f o re could not swall ow

up astron a u t s . This did not mean that the sediment was com p l e t e ly safe . Ra t h e r, the fineness of

the sediment could pose a diffe rent kind of 

h a za rd—fouling equipment and suit com p on e n t s .

Viking landers on Mars in the middle 1970s and

the recent Pa t h f i n d e r / So j o u rner mission show e d

that Mars also has a sediment coating that could

foul equipment and suit com p onents of future

M a rtian explore r s .

To d ay, it is possible to study the effects of lunar sediment on materials because the Ap o llo astron a u t s

re t u rned home with samples. Rather than con s u m e

valuable lunar sediment samples on materials tests,

a n a lysis of the sediments permitted scientists to create simulated lunar sediments to use in experi m e n t s .

Based on Viking studies of Mars and the discove ry

of Martian meteorites in An t a rc t i ca , scientists have

also created simulated Martian sediments. B o t h

s i mulants have been used in a vari e ty of tests, s u ch

as fabric abra s i on and penetra t i on of bearing seals.

Since astronaut stays on the Moon were limited to a

Teacher Tech Brief

Abrasion Tester
d ay or tw o, Ap o llo spacesuit materials on ly had to

s u rv i ve 10 to 20 hours of use. Fu t u re Mart i a n

e x p l o re r s , h ow eve r, w i ll remain on the planet for

m a ny months to a year or more, and their suits will

need to be con s t ructed of rugged materi a l s .

Purpose

This apparatus will measure the abrasion of fabrics

and other suit materials exposed to simu l a t e d

Martian sediment.

Principle

Test samples are placed in a rock tumbler or a specially constructed tumbler similar to the one shown

on the proceeding page. Simulated Martian sediment is placed in the drum and the rotating motion

causes the sediment to abrade the samples.

Materials and Tools Checklist

Wooden base (12" x 24" x 1")

Electric motor with pulley

(use motor with low rpms)

Pulley belt

Plastic food jar (1 gallon)

Four casters

Wood block stops

Fabric samples

Masking tape

Martian sediment simulant

Operation

The device shown on the previous page is a homemade rock tumbler. It is constructed from a plastic

jar of the kind supplied to cafeterias and restaurants

with various food stuffs such as relishes or mayonnaise. A motor, pulley, and rubber band belt rotate

the jar. The jar rests on inverted casters and is held

in place with stops at the ends. Squares of fabric

samples are taped to the inside walls of the jar and

a measured quantity of Martian sediment simulant

is placed in the jar. The jar is allowed to rotate for a

day or two and the fabric samples are removed for

c om p a ri s on with fresh samples. R e d d i s h - b row n

volcanic rock used for landscaping can be used for

making Martian sediment simulant. Bags of the

rock will have small amounts of abraded sediment

at their bottoms or you can crush the rocks to a fine

soil-like material. Be sure to wear eye protection

and gloves. Use a hammer to smash the rocks. Sort

out and discard the larger pieces to leave just the

sandy to powdery material behind.

Tips

• Look for an electric motor at an electric parts

store. It may also be possible to find a suitable

motor in an old appliance. Casters can be

obtained at a hardware store.

• Examine fabric samples for signs of wear such as

tears and holes. If a sample is opaque, place it on

the lighted stage of an overhead projector to look

for holes and thin areas.

• If solid materials are to be tested,do not test fabrics at the same time. The solid materials may

damage the fabric,making it difficult to interpret

the results.

• Estimate the number of rotations of the "rock

tumbler" jar by counting how many times the jar

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Fabric abrasion tester in use at the NASA Johnson Space Center. The white

drum contains an inflated cylinder made from the outer fabric ofa spacesuit.

The drum also contains lunar sediment simulant. An electric motor with a

pulley drives the drum.
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rotates in one minute. Multiply the number of

minutes the jar has been rotated by the number

of rotations per minute.

• M o re student intera c t i on with the activity ca n

take place if the motor-dri ven apparatus is

replaced with just a jar. E a ch day for a week or

tw o, students spend a few minutes shaking and

rotating the jar and counting the number of times.

Extensions

• Devise testing procedures to measure the abrasion of the fabric on fabric in places on the spacesuit where fabric rubs against itself (underarms,

crotch, etc.).

Apollo 16 astro n aut Charles M . Duke Jr. samples lunar regolith (sediment) next to the “house ro c k” in the lunar Desca rtes highlands. Very fine sediment clings to his suit.
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NASA Spacesuit

Test Apparatus

In addition to laboratory versions of the testing

apparatus described in the Teacher Tech Briefs,

NASA spacesuit engineers also employ the apparatus shown on these two pages.

Mechanical Boot Tester

Checks book performance with a walking motion.

Bearing Tester

Bearings and other joints are subjected to simulated lunar sediment to find

out ifthe sediment degrades their performance. The wrist bearing inside the

unit is rotated as simulated lunar sediment is poured over it.The white device

in the tester is a winshield wiper motor that rotates the bearing.

Waist Bearing Tester

The waist bearing is placed through a series ofbends by this device.
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Sleeve and Leg Tester

Inflated segments ofsleeves and legs are bent repeatedly by this device.

Spacesuit Robot

The forces required to move suit arms and legs when the suit is pressurized are

measured with this specialized robot.The robot is placed inside a suit.A gasket seals the neck ofthe suit.The suit is then pressurized through the robot’s

“head.”Joints in the arm and leg ofthe black side ofthe robot are bent on

command and the forces are measured. The white side ofthe robot is nonfunctioning. Only one side ofthe robot is needed for data and the white side

serves only as balance.
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Context

Gravity is an attractive force that all objects have for

one another. It doesn't matter whether the object is

a planet, a cannon ball, a feather, or a person. Each

exerts a gravitational force on all other objects

around it.

The amount of the gravitational force between two

objects is directly proportional to the product of

their two masses and inversely proportional to the

square of the distance between their centers of

mass.This relationship is expressed in the equation

below. M1 and M2 are the respective masses of the

two objects and r is the distance between their centers of mass. G is the gravitational constant.

By referring to this equation, we can see that the

f o rce of gra v i ty is not con s t a n t . The amount

depends upon local conditions. For example, an

astronaut walking on the surface of the Moon

would weigh only 1/6th what he or she would

weigh on the surface of Earth.That same astronaut

would weigh about 2/5ths as much on the surface of

Mars. The reason for the difference is that the

Moon and Mars are less massive bodies than Earth

and they have smaller radii. Less mass reduces the

amount of gravity experienced on the surface of the

Moon and Mars while the smaller radii increases it.

Besides being altered by mass and distance, our perception of gravity's pull can also be altered by

motion. Gravity can be made to appear to increase

by accelerating away from Earth, as in a rocket

liftoff or by riding on a centrifuge. Gravity can be

made to appear to decrease by falling. NASA calls

the environment created by falling microgravity.

You can get an idea of how this works by looking at

the diagram on the next page. Imagine riding in an

elevator to the top floor of a very tall building. At

the top, the cables supporting the car break, causing

the car and you to fall to the ground. (In this example, we discount the effects of air friction on the

falling car.) Since you and the elevator car are

falling together, you feel like you are floating inside

the car. In other words, you and the elevator car are

accelerating downward at the same rate due to gravExploration Brief

Different Gravity

f = G m1m2

r

2
ity alone.If a scale were present, your weight would

not register because the scale would be falling too.

The ride is lots of fun until you get to the bottom!

NASA calls this floating condition microgravity.

The condition is experienced in orbit and in transit

between planetary bodies.

A s t ronauts experience many diffe rent gra v i ty

e nv i ronments during space tra vel and these 

e nv i ronments make diffe rent demands on the

spacesuits they wear. When designing a spacesuit,

it is important to know in which gra v i ty env i ronments the suit will be worn . For example, g re a t e r

s t rain will be placed on fluid pumping systems if

the pump has to work against gra v i ty than if it

w o rks in a micro g ra v i ty situation . On an Ap o ll o

M o on landing mission , spacesuits were worn during liftoff when high G (gra v i ty) forces were fe l t

b e cause of the accelera t i on . The suits were worn

d u ring lunar walks where the gra v i ty was 1/6th

that of Earth's gra v i ty. Fi n a lly, the suits were

w o rn in a micro g ra v i ty env i ronment duri n g

s p a c ewalks while they coasted back from the

M o on . Space Shuttle spacesuits are worn on ly in

m i c ro g ra v i ty during space walks in Earth orb i t .

Suits worn on the surface of Mars may have to be

modified to function in the 2/5ths g that will be

e x p e rienced there .

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(A) The person in the stationary elevator car experiences normal weight.(B) In the car

immediately to the right, weight increases slightly because of the upward acceleration.

(C) Weight decreases slightly in the next car because of the downward acceleration.(D)

No weight is measured in the last car on the right because of freefall.
Investigation: Creating

Microgravity

Microgravity is easy to create. It is merely a matter

of dropping objects.By falling, gravity's local effects

are greatly reduced.That means that if two objects

are falling together, gravity's influence on them

becomes nearly zero. For example, if a heavy weight

is suspended from an elastic cord, the cord will

stretch out. If the cord is released, the weight and

cord begin to fall to the floor. With gravity's effects

greatly reduced, the cord immediately retracts to its

relaxed length.The following activities are methods

of creating microgravity in the classroom.

Materials and Tools Checklist

Paper cup

Masking tape

Rubber band (thin)

Several washers or nuts

Scissors

Objective

• To investigate microgravity.

Procedure

S tep 1. Cut the ru b b er band and tie one end to the nuts

or washer s . The nuts or washers should be

h e avy enough to stre t ch the ru b b er band when

suspended from the free end.

S tep 2. Tape the free end of the ru b b er band to the

inside of the cup.

S tep 3. Hold the cup upside down. Slowly tu rn the cup

right side up so that the nuts or washers hang

outside the cup.

S tep 4. Drop the cup to the floor from eye level .

O b s erve what happens to the we i g h t s .

S tep 5. Discuss the implications of m i c ro grav i ty on

s p acesuit design. For ex a m p l e, how can fluids

( w a ter cooling sy s te m , gas circ u l a t i o n , etc.) be

m o ved in micro grav i ty ?

Extensions

• Challenge students to come up with a way of

simulating the 2/5ths gravity of Mars.

• Obtain a copy of the NASA curriculum 

supplement Microgravity—Activity Guide for

Science, Mathematics, and Technology Education,

E G - 1 9 9 7 - 0 8 - 1 1 0 - H Q. The guide con t a i n s

plans and instructions for several additional

microgravity demonstrations.

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C o n t ex t

A s t ronauts on spacewalks are likely to encounter fastm oving part i cles ca lled meteoro i d s . A meteoroid is usua lly a fragment of an asteroid consisting of ro ck and/or

m e t a l . It can be ve ry large with a mass of seve ral hund red metric ton s , or it can be ve ry small—a microm e t eo roid which is a part i cle smaller than a grain of sand.

M i c rom e t e o roids are usually fragments from com e t s .

E ve ry day Earth's atmosph e re is stru ck by mill i ons of

m e t e o roids and microm e t e o ro i d s .Most never re a ch the

s u rface because they are vapori zed by the intense heat

g e n e rated by the fri c t i on of passing through the atmosph e re . It is ra re for a meteoroid to be large enough to

s u rv i ve the descent through the atmosph e re and re a ch

solid Eart h .If it does, it is ca lled a meteori t e .

In space there is no blanket of atmosph e re to pro t e c t

s p a c e c ra ft from the full force of meteoro i d s . It was

once believed that meteoroids tra veling at velocities up

to 80 kilometers per second would prove a great haza rd to spacecra ft . H ow eve r, scientific satellites with

m e t e o roid detection devices proved that the haza rd

was minimal. It was learned that the majori ty of meteo roids are too small to penetrate the hull of spacecra ft .

Their impacts pri m a ri ly cause pitting and "sandblasting" of the cove ring surf a c e .

R e c e n t ly spacecra ft debris is of great con c e rn to spacec ra ft engineers. Thousands of space launches have left

m a ny fragments of launch ve h i cl e s ,paint ch i p s , and other

"space trash" in orb i t . Most part i cles are small , but they

t ra vel at speeds of nearly 8,000 meters per secon d .T h e s e

space-age part i cles have become a significant haza rd to

s p a c e c ra ft and to astronauts on extra vehicular activities.

Engineers have protected spacecra ft from microm e t eo roids and space trash in a number of ways , i n cl u d i n g

t h i ck - w a ll con s t ru c t i on and mu l t i - l ayer shields con s i s ting of foil and hyd ro ca rb on materi a l s . A microm e t eo roid striking mu l t i - l ayer shields disintegrates into

h a rmless gas that disperses on inner wall s . Sp a c e s u i t s

p rovide impact pro t e c t i on through various fabri c - l aye r

c om b i n a t i ons and stra t e g i ca lly placed rigid materi a l s .

Although effe c t i ve for part i cles of small mass, t h e s e

p ro t e c t i ve strategies do little if the part i cle is large. It is

e s p e c i a lly important for spacewalking astronauts to be

ca reful when they repair satellites or do assembly jobs

on the Intern a t i onal Space St a t i on . A lost bolt or nut

could damage a future space mission through an accidental coll i s i on .( No t e : Low orbit tends to be cl e a rer of

p a rt i cles than higher orbits because low orbit part i cl e s

tend to decay and burn up in the atmosph e re.) 

Exploration Brief

Micrometeoroids and Space Debris
Investigation

Pea Shooter Meteoroids

The effects of high-speed micrometeoroid impacts

can also be simulated with a "pea shooter." The

shooter is actually a plastic milkshake straw. The

projectile can be dried peas, popcorn, dried lentils,

etc. The object of the activity is to penetrate tissue

paper with the pro j e c t i l e . As with the Po t a t o

Astronaut activity, the velocity of the impactor

determines the penetration.

Materials and Tools Checklist

Plastic milkshake straw 

Dried peas, popcorn, etc.

Tissue paper (for wrapping presents)

Cardboard box

Tape

Eye Protection

Objective

• To compare the effect on tissue paper penetration

between low and high speed projectiles.

Procedure

Step 1. Cover the opening of a box with tissue paper.

Stretch the paper tight.

Step 2. Drop a pea or other projectile from a distance

of approximately 1 meter on to the tissue

paper. Does the pea penetrate?

Step 3. While wearing eye protection, stand back a

few meters from the box and blow the pea

through the pea shooter at the tissue paper.

Does the pea penetrate? (With a little prac -

tice, the pea should penetrate the paper.)

Step 4. Investigate what happens when more than

one layer of tissue paper is used to cover the

box opening.

Safety Precautions

Students must wear eye protection. Caution students not to inhale through the straw.

Connections: Mathematics

Refer to the "Potato Astronaut–Part One" activity

that follows.

Extensions

• Tape two straws end to end. Does that increase

the velocity of the projectile?

• Experiment with projectiles that have a greater

mass than the pea.

• Add a second layer of tissue paper to the box to see

what effect the second layer has on penetra t i on .

• Is there any relationship between the ability to

penetrate the tissue paper and the distance the

shooter stands from the box?

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Investigation

Potato Astronaut—Part One

The effects of high-speed micrometeoroid impacts

are simulated with a potato and a straw. Students

hold the potato in one hand and stab it with the

other using a plastic milkshake straw. The penetration depth into the potato relates to the speed of the

stabbing action. A straw slowly pushed into the

potato collapses. The plastic isn't strong enough to

support the force exerted at the opposite ends of the

straw. However, when the straw is thrust rapidly

into the potato, the straw easily penetrates and

passes through. The straw enters the potato before

it has a chance to collapse. As it enters, the surrounding potato helps support the straw by shoring

up its sides.

Materials and Tools Checklist

Potato

Plastic (milkshake-size) straw 

Objective

• To investigate the relationship between velocity

and penetration depth when a potato is struck with

a plastic straw.

Procedure

Step 1. Hold a raw potato in one hand. (See illustra -

tion.) While grasping the straw with the other

hand, stab the potato with a slow motion.

O b s erve how deeply the straw penetra tes 

the potato.

S tep 2. Repeat the ex p eriment but this time stab the

p o tato with a fast motion. O b s erve how deeply

the straw penetra tes the pota t o. C o m p a re your

o b s ervations with the results of s tep 1.

Safety Precautions

Be careful to hold the potato as illustrated so that

the straw does not hit your hand. Work gloves will

provide additional protection.

Connections:Mathematics

The kinetic energy output of an impact, given in

Joules, is calculated with the following equation:

KE = 1/2mv

2

m = mass of impacting object

v = velocity of impacting object

Note: The mass in this activity is actually the combined mass of the straw and the hand and forearm

driving it.

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Investigation

Potato Astronaut—Part Tw o

In part one of Potato Astronaut, students found

that "high speed" impacts enabled the plastic straw

to penetrate the potato without coll a p s i n g.

Challenge the students to design a way to protect

the potato from damage caused by impacts using

just the materials they brought to the classroom.

Their solutions to the challenge should be flexible

and light in weight.

Materials and Tools Checklist

Plastic (milkshake-size) straw 

Potato

Tissue paper, notebook paper, handkerchiefs,

rubber bands napkins, aluminum foil, w a x

paper, plastic wrap, etc.

Impact Resistance Test Stand (from Teacher

Tech Brief )

Procedure

Step 1. S tudents design a method for pro tecting pota t o

a s tro n auts from damage caused by the plastic

s traw when the straw is quickly stabbed into

the pota t o.

Step 2. Af ter students have te s ted a method for pro te c t -

ing a pota t o , conduct a discussion to eva l u a te

te chnologies devel o p e d. R efine the constra i n t s

for a pro tection sy s tem (e. g. the materials used

must toge t h er be no thicker than mm).

Step 3. Have students redesign their system based on

the refined constraints. Conduct additional

impact tests with the straw.

Step 4. Test pro tection sy s tems by using the an

Impact Resistance Test Stand as described in

the Teacher Tech Brief found earlier in the

guide. Evaluate the effectiveness ofthe protec -

tion systems developed.

Extensions

• Compare technologies for protecting astronauts

from micrometeoroid and space debris impacts to

other protective technologies such as bullet-proof

vests, suits of armor, shields on power tools, and

windshields on vehicles. How does the function

d e t e rmine the form? (e.g. M o t o rcycl e

helmet–provide protection during crash . . . be

streamlined . . . comfortable to wear . . . protect

face from bug and rock impacts, etc.)

• E x p e riment with diffe rent fabrics and fabri c

combinations for protective garments.
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C o n t ex t

It is not sufficient for the health and well-being of an

a s t ronaut just to be protected from the haza rds of the

e nv i ronment in which he or she is trying to work .It is

also necessary to consider the con d i t i ons that are created by the suit itself. One of the most important of

these con d i t i ons is tempera t u re . Suit insulation technologies protect the astronaut from extreme high and

l ow tempera t u res of the space env i ron m e n t .H ow eve r,

the same insulation tech n o l o gy also works to keep

heat released by the astronaut's body inside 

the suit. To get an idea of what this is like, i m a g i n e

walking around in summer wearing a plastic bag. Fo r

this re a s on , an active cooling system is employe d .

In Space Shuttle Extra vehicular Mobility Units or

EM Us , the cooling system consists of a netw o rk of

s m a ll diameter water circ u l a t i on tubes that are held

close to the body by a Spandex® body suit. H e a t

released by the astronaut's body movements is tra n sfe r red to the water where it is ca r ried to a re f ri g e ra t i on

unit in the suit's back p a ck . The water runs across a

p o rous metal plate that is exposed to the vacuum of

outer space on the other side. Sm a ll amounts of water

pass through the pores where it fre ezes on the outside

of the plate. As additional heated water runs across the

p l a t e, the heat is absorbed by the aluminum and is

c onducted to the exposed side. T h e re the ice begins to

s u b l i m a t e, or turn dire c t ly into water vapor and disperses in space. Su b l i m a t i on is a cooling pro c e s s .

Ad d i t i onal water passes through the pore s , and fre eze s

as before . C on s e q u e n t ly, the water flowing across the

plate has been cooled again and is used to re c i rc u l a t e

t h rough the suit to absorb more heat.

Supplementing the EMU cooling system is an air 

c i rc u l a t i on system that draws perspira t i on-laden air

f rom the suit into a water separa t o r. The water is

added to the cooling water re s e rvoir while the drier air

is re t u rned to the suit.Both the cooling system and the

air- circ u l a t i on system work together to con t ribute to

a com f o rtable internal working env i ron m e n t . T h e

w e a rer of the suit con t rols the operating rates of the

s ystem through con t rols on the Display and Con t ro l

Module mounted on the EMU ch e s t .

Ob j e c ti ve

• To investigate and experience the way the water

cooling system in the Space Shuttle EM U

f u n c t i on s .

Exploration Brief

Keeping Your Cool
Investigation

Water Cooling—Part One

This demonstration shows the principle behind the

operation of the Space Shuttle EMU liquid cooling

garment.Instead of an internal heat source (the suit

wearer), the heat is provided by a strong electric

light bulb or flood lamp.

Materials and Tools Checklist

Two coffee cans with plastic lids

4 meters of aquarium tubing

Two buckets

Two thermometers

Duct tape

Water (solid and liquid)

Heat source (light bulb and fixture)

Hole punch

Flood light and fixture

Procedure

Step 1. Punch a hole near the bottom of the wall of a

metal coffee can. The hole should be large

enough to pass aquarium tubing through.

Punch a second hole in the plastic lid ofthe can

so that tubing can pass through it as well.

Punch another hole in the center of the lid so

that a thermometer will fit snugly into it.

Finally, punch a hole in the center of the sec -

ond coffee can lid for another thermometer.

Step 2. Loosely coil the aquarium tubing and place it

inside the first coffee can. Use bits of tape to

hold the coils to the walls and to keep them

spread out evenly. Pass the lower end of the

tube through the hole in the can wall and the

upper end through the outer hole in the lid.

The lower tube should extend to the catch

bucket that will be placed below the can.The

upper end will have to reach to the bottom of

the ice water bucket.That bucket will be ele -

vated above the can.Insert thermometers into

each can.

Step 3. Place the two cans on a table top. Direct the

light from a strong light bulb or flood light to

fall equally fall on the two cans. The light

should be no more than about 25 centimeters

away from the cans. Fill a bucket with ice

water and elevate it above the two cans.Place

the catch bucket below the two cans.

Step 4. Turn on the light. Observe and record the

temperatures on the two thermometers. After

two minutes, again observe and record the

temperatures.

Step 5. Place the upper end of the aquarium tubing

into the ice water and suck on the other end of

the tube to start a siphon flowing. Let the

water pour into the catch bucket.

Step 6. Observe and record the temperature ofthe two

cans at regular intervals for ten minutes.

Tips

• If more than one student is going to start the

siphons with sucking on the end of the tube,

make sanitary mouthpieces like those called for

in the activity "O2How Much?"

• Color the water with food coloring to increase its

visibility in the siphons.

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Water flow to

catch basin

Siphon from ice water bucket
Assessment

Have students design a graph to display the data

collected in step 6.

Extensions

• How can the flow of icy water be con t ro lled? Find a

w ay to maintain a constant tempera t u re inside the ca n

with the tubing.M ove the light source closer to the ca n

so that it is heated more than before . Try to maintain

the internal tempera t u re at the same level as before .

Investigation

Water Cooling —Part Two

This demonstration permits students to experience

the water cooling technology used in the Space

Shuttle EMU.

Materials and Tools Checklist

Two buckets 

3 meters of aquarium tubing

Water (solid and liquid)

K i t chen size plastic garbage bag (one per student)

Procedures

Step 1. Distribute one plastic garbage bag to each

student. Have students wearing long-sleeve

shirts roll up one sleeve.

Step 2. Ask each student to place their bare arm inside

the bag and then gather the plastic so that it

fits closely along the entire length of the bag.

Tell students to repeatedly make a fist or wave

their arm while it remains in the bag for a for

two minutes. (Steps 1 and 2 can also be done

with plastic gloves.)

Step 3. After two minutes, have students remove

their arms from the bags and observe any 

sensations that come with their re m o va l .

Discuss what students felt. Make sure they

understand that a spacesuit, like the plastic

bag, retains body heat. Also discuss why their

a rms suddenly felt cooler with the re m o val of

the ba gs .(Wa rm air in the bag was released and

m o i s tu re from per s p i ration began evap o ra t i n g.) 

S tep 4. S elect a student vo l u n te er for another ex p eri -

m e n t . Wrap the middle of the length of a q u a ri -

um tubing around the ba re arm of the vo l u n te er

s everal times.

Step 5. Start a siphon flow from the ice water bucket

through the tube. Ask the student to describe

for the rest of the class the sensations he or she

feels. (See note about mouthpiece in part 1.)

Extensions

• Discuss how a liquid cooling garment could be

c on s t ructed that could operate con t i n u o u s ly

without siphons and buckets of ice water that

eventually run out.

• What professions on Earth might find liquid

cooled garments useful? 

• Design and construct a liquid cooling garment

out long underwear or Spandex® running tights.

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Context

The tempera t u re range of outer space and on plane t a ry bodies is affected by a wide range of factors.

In outer space, the tempera t u re on a surf a c e

depends upon whether that surface is in sunlight

and if so, the angle of that surface to the Sun's rays .

On a planetary body, the tempera t u re also vari e s

with the ambient atmosph e ric tempera t u re, w i n d s ,

and nearby surface materi a l s . For example, on

E a rth tempera t u res can vary dra m a t i ca lly on a

summer day between asphalt parking lots and

g rassy bord e r s .

When designing spacesuits, it is important to

account for the tempera t u re range of the env i ronment for which the suit is intended. Heating and

cooling systems inside a suit can moderate tempera t u re s , but electric power to operate these sys t e m s

limits the length of time the suit can be used before

re ch a r g i n g. One way to reduce the dependency of a

spacesuit heating/cooling system is to use materi a l s

for suit con s t ru c t i on that have desirable therm a l

p ro p e rt i e s . I f, for example, a suit is operated in a

ve ry cold env i ron m e n t , good insulating materi a l

w i ll reduce the need for internal suit heating.

Materials and Tools Checklist

Coffee cans with plastic lids

Thermometers

Flood lamp (optional)

Various colors of paint

Foil, construction paper, etc.

Clock

Refrigeration (see step 6)

Objective

• To investigate the effect different colors, reflective

surfaces, and different materials on radiant heat

absorption and heat radiation.

Investigation

Surface Color

This activity investigates the affect surface color has

on heat absorption and radiation.

Procedure

S tep 1. Paint the surf aces of s everal coffee cans in

d i f f erent colors such as white, bl ac k , gre e n ,

or yel l o w.

Exploration Brief

Absorption and Radiation
Step 2. Punch a small hole in the plastic resealable lid

and insert a thermometer bulb to approxi -

mately the middle of each can.

Step 3. Place the cans in sunlight so that all are

equally exposed. Immediately record the ini -

tial temperature of each can. If you are doing

the experiment inside, expose the cans to a

flood light. It is important that each can

receives the same amount of heat from the

lamp. Measure and record the temperature of

the cans every minute.

Step 4. Remove the cans from the heat source after 10

minutes and measure and record their tem -

peratures again for the next 10 minutes.

Graph your data. Relate the temperature rise

and fall of each can to its surface color.

Step 5. Change the surface material of the cans by

wrapping them with aluminum foil, gray

construction paper,or cloth.Repeat the exper -

iment to find the best combinations of colors

and surfaces for different environments.

Step 6. Repeat the experiment by subjecting the cans

to intense cold. The cans can be placed in a

freezer or in a tub with ice water or a block of

dry ice.

Investigation

Insulating Layers

In this activity, students explore the insulative properties of several materials.

S tep 1. S tack different fabri c s , p ap er, and foils, a n d

fold them into small envel o p e s . I n s ert a ther -

m o m e ter and repeat the previous ex p eriment to

d e termine the heat absorption and ref l e c t i o n

p ro p erties of d i f f erent material combinations.

Extensions

• C onduct ch rom a t o g ra phy experiments on various ink colors to see what their com p onent colors are . B l a ck inks often consist of seve ral colors.

The re a s on for mixing seve ral ink pigments is to

make a darker black (more complete absorp t i on

of light). (The Space Shuttle uses black heat

shield tiles on the bottom of the orbiter to quickly dissipate the heat produced when re e n t e ri n g

E a rth's atmosph e re . )

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Context

In spite of many decades of experience in developing and evaluating spacesuits,they are still fatiguing

to wear. The internal pressure of the suit creates

resistance to movements of the arms, hands,or legs.

Consequently, astronauts training for a spacewalk

are encouraged to stay in excellent physical condition by training on the ground for endurance and

strength. After a spacewalk, crew members are

allowed a day of rest before going out again.That is

why missions,such as the multi-day servicing of the

Hubble Space Telescope, have two EVA crews that

alternate spacewalk days.

The exhaustion factor of spacesuits can be mitigated

s om ewhat by insuring that the suit the crew member will wear in space fits pro p e rly. It is essential that

the position of suit joints pre c i s e ly match the posit i on of shoulders, e l b ow s , wri s t s , k n u ck l e s , k n e e s ,

and ankles. A misalignment of a mere centimeter in

the arm length, for example, can lead to aching 

fingers after a seve ral-hours spacew a l k i n g.

Getting the right fit is com p l i cated by a number of

f a c t o r s . It is important that the suit fits when it is

p re s s u ri ze d . An unpre s s u ri zed suit is slightly small e r

than when it is pre s s u ri ze d . The suit must fit ri g h t

when the crew member is in space. The micro g ra v i ty

Exploration Brief

Getting the Right Fit
e nv i ronment experienced in Earth orbit affects the

human body in many ways . One effect is spine

l e n g t h e n i n g. In one G (gra v i ty ) , the ve rt e b rae of the

spine are close together but are kept separate by 

ru b b e ry disks that act as shock absorb e r s . In space,

without the perc e i ved dire c t i onal force of gra v i ty, t h e

disks expand slightly, causing the ve rt e b rae to move

s l i g h t ly farther apart than they are when the crew

member is standing upright on Eart h . This spinelengthening causes the astronaut to get tall e r, re s u l ting in arm joint misalignment. Spine lengthening in

m i c ro g ra v i ty has to be accounted for when astron a u t s

a re measured for their suits. The typ i cal astron a u t

w i ll gain between 2 and 3 centimeters in height while

in space.

To avoid the expensive and time-consuming pro c e s s

of creating custom-made suits for astron a u t s , a s

NASA did during the Ap o llo mission s , suits with

i n t e rchangeable parts are used. D i f fe re n t - s i ze d

upper and lower torsos are available, but arm and

leg lengths are still difficult to match. NASA has

solved this problem for the Shuttle EMU by creating sizing inserts that are added or removed from

the restraint layer in the arms and legs to achieve

the right fit.The inserts are fabric rings of different

lengths that are laced into the arms and legs.

Selecting the right combination of inserts insures

the best fit possible.

Objective

• To experience the measurement process used in

sizing a spacesuit arm to fit different wearers.

Materials and Tools Checklist

PVC thin-wall sewer pipe (4 in. dia.)

Saw (crosscut or hacksaw)

Measuring tape or ruler (metric)

Duct Tape

Vinyl clothes-dryer hose

Scissors

Thick rubber gloves

Sand paper or knife

Procedure

Step 1. Construct a variety of spacesuit arm segments

by sawing off measured lengths of PVC plas -

tic thin wall sewer pipe. (See the tip section

for information on where the sewer pipe and

other needed materials can be obtained.) Cut

the pipe into segments 25, 50, 75, and 100

mm long. Cut two of each size. Cut three

additional segments of the 50 mm length.

Step 2. Create a suit elbow joint by connecting two of

the 50 mm segments with a 25 cm piece of

vinyl clothes dryer hose. Slip the hose ends

over one end of each ofthe segments.It will be

necessary to the hose a small amount to accom -

plish this task. Fasten the hose to the segments

with duct tape.

Step 3. Slip the cuff of one ofthe gloves over a 50 mm

pipe segment. The fit may be tight but try to

slide the ring in so that it just reaches the posi -

tion of the wrist.Trim off the excess of the cuff

so that the glove can be affixed to the ring

with duct tape.

Activity

Step 4. Provide the rings, joint, glove, measuring

tape, and duct tape to a group of students. Tell

the students to select one member of their

group to serve as the astronaut. Their objec -

tive is to fit a suit arm to that astronaut.The

students should begin by measuring the arm

and mapping the range of movement of the

arm without the suit. Use the Arm Range of

Movement Data Sheet for recording data.

Step 5. The students should select the right combina -

tion of segments to use to construct the arm.

PVC rings are joined with pieces of duct tape.

Step 6. After completing the arm, the student group

should test it by placing the "astronaut's" arm

into the suit arm.They will then evaluate the

arm by repeating the range of movement tests

done before and by asking the astronaut how

comfortable the arm is to wear. If the fit is not

comfortable or the range of movements are

7 8 • Suited for Spacewalking An Activity Guide for Technology Education, Mathematics, and Science, EG- 1 9 9 8 - 0 3 - 1 1 2 - H Q
restricted, the student group should adjust the

arm length by changing the lengths of the

PCV rings used. When the fit is comfortable,

and the range of movement is acceptable,

record the sizing data in the log chart that is

provided. The sizing process can be repeated

with a different student.

Tips

• All the materials for this guide can be obtained at

larger hardware stores. Pick a thin wall sewer

pipe without holes in its sides. A 10 foot length

of pipe is inexpensive and will provide material

for several sets of arms.

• A long sleeve shirt worn by the astronaut will

reduce any possibility of pinching skin between

pipe segments.

• Use the saw to cut the sewer pipe.Have someone

help you hold the pipe as you cut it. Use sandpaper or a sharp knife to remove burrs left on the

pipe segments after sawing.

• Duct tape pieces can be removed and used again

for joining segments. White duct tape can be

substituted for gray tape to improve the appearance of the arms or one inch wide masking tape

can be used.

• Actual arm measurements for spacesuit fitting

involve more measurements than just arm length

and range of movement of the extended arm in

t h ree planes. Other necessary measure m e n t s

include upper and forearm circumference, hand

and finger size, knuckle location, and movement

of the forearm from the elbow.

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Arm Range of Movement Data Sheet

Subject Name:

Arm Length cm (shoulder to elbow)

Arm Length cm (elbow to wrist)

X-Z Plane Movement Range:

0 to +

0 to -

X-Y Plane Movement Range:

0 to +

0 to -

Y-Z Plane Movement Range:

0 to +

0 to -

0

30

60

90

-30

-60

-90

-120

-150

120

150

+180 -

-90

+180

-

90

0

30

60

-30

-60 -120

-150

120

150

-60 -120

30

60

90

-30

-90

-150

120

150

+180 0 -
Extensions

• When fitting spacesuit components to astronauts, more than 100 measurements are taken.

Set up a measuring activity with students and

determine the class average for each measurement made. Because of certain sensitivities, you

may wish to avoid girth measurements. Refer to

the chart on the next page for data covering girth.

Measurements on the chart provide the range of

m e a s u rements between the 5th percentile 

( 4 0 - year-old Japanese female) and the 95th 

percentile (40-year-old American male). These

range measurements are projections to the year

2000 in a one-gravity environment.

• Create a computer spreadsheet to compile class

data.

Suited for Spacewalking An Activity Guide for Technology Education, Mathematics, and Science, EG-1998-03-112-HQ • 8 1

A

B

C

D

E

FG

H

J

L

N

P Q

R

S

U

T

V

I

O

K

M
8 2 • Suited for Spacewalking An Activity Guide for Technology Education, Mathematics, and Science, EG- 1 9 9 8 - 0 3 - 1 1 2 - H Q

Body Size Range Measurements

Based on 1989 Man-Systems Integration Standards, NASA-STD-3000

Category Minimum (cm) Maximum (cm)

A. Stature* 162.1 187.7 

B. Vertical trunk dimension 64.3 74.4

C. Crotch height 74.4 91.9

D. Knee Height 32.3 38.9

E. Wrist to wrist distance 131.6 167.1

F. Elbow to elbow distance 85.9 106.2

G. Chest breadth 27.9 36.6

H. Head breadth 12.7 16.5

I. Hip breadth 32.3 38.9

J. Arm reach 80.5 94.2

K. Shoulder to wrist reach 62.2 73.7

L. Chest depth 21.3 27.7

M. Head depth 18.3 21.6

N. Chin to top of head 21.8 24.4

O. Hip depth 24.1 29.2

P. Foot length 21.1 27.4

Q. Foot width 8.9 10.7

R. Thigh circumference† 52.1 67.1

S. Biceps circumference (flexed) 27.4 36.8

T. Chest circumference 89.2 109.7

U. Instep NA 8.3

V. Head circumference 55.5 60.2

* Stature increases approximately 3 percent over the first three to four days in microgravity. Because

almost all the change appears in the spinal column, other dimensions such as vertical trunk dimension

increase proportionately.

† Thigh circumference will significantly decrease during the first day in orbit due to the shift of fluid to

the upper torso.
Suited for Spacewalking An Activity Guide for Technology Education, Mathematics, and Science, EG-1998-03-112-HQ • 8 3

Context

A typ i cal extra vehicular activity (EVA) lasts about 7

h o u r s . Du ring that time, an astronaut perf o rms a

number of activities, s ome of which are ve ry stre n uo u s . To make it possible to accomplish the mission ,

the spacesuit has to provide a steady and re l i a b l e

oxygen supply for breathing and suit pre s s u ri za t i on .

The oxygen supply in the pri m a ry life - s u p p o rt 

s ystem (PLSS) is contained in four oxygen tanks.

Two of the tanks are used as the pri m a ry ox y g e n

s u p p ly and two for an emergency secon d a ry supply.

The two pri m a ry tanks each have a volume of 3,980

c m3. T h ey contain a total of 0.55 kilograms of 

oxygen at a pre s s u re of 5,860.5 kilopasca l s . As this

oxygen circulates through the suit, it passes thro u g h

a re cycling system that re m oves ca rb on diox i d e,

o d o r s , and humidity. The two secon d a ry ox y g e n

tanks have a volume of 1,460 cm3 and contain a

total of 1.19 kilograms of oxygen at a pre s s u re of

41,368.5 kilopasca l s . This supplies on ly enough ox ygen for about 30 minutes because this oxygen is not

c on s e rved and re cycl e d .

Although the Shuttle spacesuit is used in Eart h

o rbit where the suit is in effe c t , w e i g h t l e s s , t h e

oxygen tanks still have to be con s t ructed from

l i g h tweight materi a l s . Weight is not a problem in

o rb i t , but it is a problem for Shuttle lift o f f. T h e

Space Shuttle can ca r ry on ly so mu ch mass to

o rb i t . Lighter tanks means that additional payl o a d

can be ca r ri e d .

To reduce their weight tanks are made from thinw a ll metal shells that are wrapped with Kevl a r ®

filaments and resin for stre n g t h .

Objective

• To measure the quantity of oxygen a person will

need under varying levels of activity

Materials and Tools Checklist 

Two-liter soft drink bottle

1 meter of flexible plastic tubing 

(from a hardware or aquarium store)

Permanent marker

Paper strips

Cellophane tape

Water 

Large pot or aquarium

Exploration Brief

O2—How Much?
Procedure

Step 1. Obtain the materials in the material list and

begin by calibrating the 2 liter soft drink bot -

tle. Stand the bottle upright and pour mea -

sured amounts of water into the bottle with a

beaker. Add 100 ml and mark the side of the

bottle at the top surface of the water. Repeat

this procedure until the bottle is filled.

Step 2. Make paper mouthpieces by rolling a strip of

paper around one end of the tube. Use a small

strip of tape to hold the mouthpiece together.

Make a new mouthpiece each time a different

person uses the apparatus.

Step 3. Partially fill a large pot or aquarium with

water. Fill the bottle with water and invert it

in the aquarium. Support the bottle by hold -

ing it with one hand around the neck. Insert

the air hose into the bottle neck. Attach a

mouthpiece to the other end of the tube and

have a student fully exhale a normal breath of

air through the tube. Water will be driven out

of the bottle. Read the volume of air trapped

inside the bottle from the calibration marks

placed on the bottle's side in step 1.

Activity

Step 4. Measure the air quantity required in normal

b reathing by several vo l u n te er stu d e n t s .

Begin with the students at rest. With a fresh

mouthpiece on the tubing, have a student

inhale a normal breath of air and exhale the

air through the tube. The student should do

this several times. Measure the amount of air

in the bottle and divide this quantity by the

number of breaths.Record the quantity for "at

rest" on a data table or computer spread sheet.

Also measure and record how long it took for

the test.

Step 5. After recording "at rest" breathing require -

ments, refill the bottle with water and have

each student perform a moderate amount of

activity such as lifting small barbells for a

minute or two. After exercising, repeat the air

q u a n t i ty re q u i rement measurements and

record the numbers in the data table for "mod -

erate work."

Step 6. Repeat the procedure a third time, but have

the students run in place for a minute or two

before taking the measurements. Record the

results under "strenuous exercise."

Step 7. Discuss possible ways to determine how much

air an average "student astronaut" will need

on a 7-hour spacewalk in which the work

level will range from moderate to strenuous

and calculate an answer from the data collect -

ed. Make sure the students realize that not

only will the quantity of air taken in with

each breath changes but the breathing rate

will change with exercise. Determine what

the quantity would be if, instead of a normal

air mixtu re, p u re ox y gen would be used.

(Normal air contains 20 percent oxygen.)

Extensions

• D e t e rmine the actual volume of oxygen ca r ried in

the Shuttle spacesuit pri m a ry and secon d a ry 

oxygen supplies. Ox y g e n , under standard con d it i on s , has a mass of 1.327 kilograms per cubic

m e t e r. (The pri m a ry and secon d a ry oxygen systems contain a total of 1.74 kilograms of ox y g e n .

Divide that number by 1.327 to get the volume of

oxygen in cubit meters. Although the volume may

seem small , remember that oxygen is re cycl e d . )

8 4 • Suited for Spacewalking An Activity Guide for Technology Education, Mathematics, and Science, EG- 1 9 9 8 - 0 3 - 1 1 2 - H Q
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Context

While pre s s u re is essential to astronaut surv i v a l , t h e

p re s s u re exe rted by a spacesuit does not have to match

sea level pre s s u re on Eart h .If the atmosph e re inside a

spacesuit is pure ox y g e n , a pre s s u re equal to about on e

t h i rd sea level pre s s u re (about 33 kilopascals) is suffic i e n t . H ow eve r, s u ch low pre s s u res re q u i re a seve ra l

hour oxygen pre b reathing period to eliminate 

n i t rogen from the spacewalker's blood stre a m . If a

higher suit operating pre s s u re can be ach i eve d , a n

a s t ronaut can don a suit and immediately exit the

s p a c e c ra ft for a spacew a l k .

O p e rating pre s s u res inside spacesuits are ach i eved by

c reating some sort of pre s s u re shell around the astron a u t .The shell can be made of rigid materials or a comb i n a t i on of fabrics provided they are nearly leakpro o f.

The pre s s u re layer of the Space Shuttle spacesuit enca s e

the astronaut inside a human-shaped bag which has an

inner layer of rubber and an outer layer of nyl on .T h e

rubber contains the atmosph e re and the nyl on preve n t s

the rubber from inflating beyond a pre d e t e rmined size

and shape. Once the suit is fully inflated, a d d i t i onal gas

p re s s u re supplied to the suit pushes inw a rd on the

a s t ronaut providing a livable pre s s u re env i ron m e n t .

Objective

• To demonstrate one method for creating a workable pressure inside a spacesuit.

Materials and Tools Checklist

0.5 m ripstop nyl on (available in fabric store s )

Sewing machine

Scissors

Long balloon

Bicycle pump with pressure gauge

Small adjustable screw type, hose clamp

Tire valve

Screwdriver

Procedure

Step 1. Using two pieces of ripstop nylon,stitch a bag

as shown in the pattern on the next page. The

pattern should be doubled in size. For extra

s tre n g t h , s t i t ch the bag tw i c e. Tu rn the

stitched bag inside-out.

S tep 2. Slip the nozzle of a long balloon over the

fat end of the tire va l ve. Slide the other end

o f the balloon inside the bag so the neck of

the tire va l ve is aligned with the neck of

the ba g.

Exploration Brief

Keeping the Pressure On
Step 3. Slide the adjustable hose clamp over the bag

and tire valve necks. Tighten the clamp until

the balloon and bag are firmly pressed against

the tire valve neck. This will seal the balloon

and bag to the valve.

Activity

Step 4. Connect the tire valve to the bicycle pump and

inflate the balloon. The balloon will inflate

until it is restrained by the bag. Additional

pumping will raise the pressure inside the bal -

loon. Check the tire pressure gauge on the

pump (use separate gauge if necessary) and

pressurize the bag to about 35 kilopascals 

(5 pounds per square inch).The tire valve can

be separated from the pump so that the bag

can be passed around among the students.

Step 5. Discuss student observations of the stiffness of

the pressurized bag. square inch). What prob -

lems might an astronaut have wearing a

pressurized spacesuit?

Extensions

• C om p a re the tech n o l o gy for pre s s u ri z i n g

spacesuits to the tech n o l o gy for pre s s u ri z i n g

a u t omobile tire s .

8 6 • Suited for Spacewalking An Activity Guide for Technology Education, Mathematics, and Science, EG- 1 9 9 8 - 0 3 - 1 1 2 - H Q

Magnified view of

tire valve and clamp

One-half size pattern

for step 1
Suited for Spacewalking An Activity Guide for Technology Education, Mathematics, and Science, EG-1998-03-112-HQ • 8 7

Context

Maintaining proper pressure inside a spacesuit is

essential to astronaut survival during a spacewalk.A

lack of pressure will cause body fluids to turn to gas,

and resulting in death in a few seconds.While making spacewalks possible, pressure produces its own

problems. An inflated spacesuit can be very difficult

to bend. In essence, a spacesuit is a balloon with an

astronaut inside.The rubber of the balloon keeps in

oxygen that is delivered to the suit from pressurized

oxygen tanks in the backpack. But, as pressure

inside the balloon builds up, the balloon’s walls

b e c ome stiff, making normal bending motion s

impossible. Lack of flexibility defeats the purpose

of the spacewalk–mobility and the ability to do

work in space.

Spacesuit designers have learned that strategically

placed breaking points at appropriate locations outside the pressure bladder (the balloon-like layer

inside a spacesuit) makes the suit become more

bendable.The breaking points help form joints that

bend more easily than unjointed materials. Other

techniques for promoting bending include stitching

folds into the restraint layer that spread apart and

contract with bending and building joints into the

restraint layer like ribs on vacuum cleaner hoses.

Objective

• To observe how an external joint in a spacesuit

arm segment increases bendability of the segment.

Materials and Tools Checklist 

Two long balloons

3 heavy-duty rubber bands

Procedure

S tep 1. I n f l a te a long balloon and tie it off. The ba l l o o n

re p resents the pre s s u re bl ad d er of a spacesuit arm .

Let students try to bend the balloon in the middle.

S tep 2. I n f l a te a second long ba l l o o n . As you are inflat -

ing the ba l l o o n , slip heavy - d u ty ru b b er ba n d s

o ver the balloon at intervals so that as inflation

continues the balloon is pinched by the ru b b er

ba n d s . It is easier to accomplish this by pre -

inflating the ba l l o o n . It may be necessary to

d o u ble the ru b b er band to pinch the ba l l o o n

enough for the demonstra t i o n . Have stu d e n t s

c o m p a re the force re q u i red for bending this ba l -

loon with the force needed for the first ba l l o o n .

Exploration Brief

Bending Under Pressure
Extensions

• Compare the stiffness of the balloons to other

inflated structures such as air mattresses, inner

tubes, beach balls, etc.

• Use a Slinky® as an alternative to the rubber

bands. Place the Slinky® on a desk top and pick

up one end. Slip in the balloon and inflate it. As

the balloon inflates, it will be pinched in a spiral

pattern by the Slinky®. The pattern will achieve

the same result as the rubber bands.

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1. Suit Arm and Leg Bending Tester

Idea Bank

Electric Motor Pulley

Reciprocating Rod

Inflated Arm

Segment

Use these ideas as suggestions for additional testing

and measurement apparatus and for techniques that

could be employed for constructing suit parts.
2. Tethers

3 . Field of Vision Tester for Helmet Vision Design

D e t e rmine how mu ch visibility is needed for a space

suit helmet by measuring the field of vision of stud e n t s . Two diffe rent ways for doing this are show n .

4. Connector Seal Test

Place Martian sediment simulant or other dry

sandy sediment in the jar. Place plastic tape over the

zone where the lid comes together with the jar.

Shake the jar several hundred times and then

remove the tape to see if any sediment made its way

through the jar and lid threads to stick to the tape.

5. Weightlifting

Research an exercise routine that can be used to

strengthen the upper body. This is the area of the

body that receives the greatest workout during a

s p a c ewalk in Earth orb i t . Design exe rcises for

strengthening the lower torso and for planetary surface exploration.

9 0 • Suited for Spacewalking An Activity Guide for Technology Education, Mathematics, and Science, EG- 1 9 9 8 - 0 3 - 1 1 2 - H Q

Omnidirectional test. Use

clear plastic punch bowl

and place dots at limit of

vision.

Test for Right and

Left Views
6.Measurements for Space Helmet

7. Paper Maché Space Helmet

Inflate a large round balloon to a diameter greater

than student heads. Cover the balloon with four

layers of paper maché. Paper maché can be made

with newspaper strips and a 50/50 solution of white

glue and water or with premixed wallpaper paste.

Let each layer dry before applying the next one.

When completely dry, deflate and remove the balloon and cut appropriate holes with a scissors.Paint

as desired.

8. Visor Light Transmission Tester

C onnect a solar cell to a potentiometer and a 

m i ll a m m e t e r. These items are available from an elect ronic parts store . Adjust the potentiometer so a light

s o u rce you are measuring does not dri ve the needl e

off the sca l e .Place potential space helmet visor material between the light source and the solar cell to

evaluate the materi a l’s light-filtering pro p e rt i e s .

Suited for Spacewalking An Activity Guide for Technology Education, Mathematics, and Science, EG-1998-03-112-HQ • 9 1

30 cm
9. Vacuum Experiment - 1

Obtain an electric doorbell,push button, and doorbell transformer. Insert the wires to the doorbell

through a single-hole rubber stopper. The stopper

should fit the upper hole in the bell jar. Fill the rest

of the stopper hole with hot glue from a hot-glue

gun to seal the wires in place. Evacuate the bell jar

and ring the doorbell. While holding the button,

gradually let air back into the jar. The bell cannot be

h e a rd ringing when the jar is evacuated eve n

though the clapper can be seen to be moving. This

demonstration explains why spacesuits have 2-way

radios. Sound is not conducted through a vacuum.

10. Vacuum Experiment - 2

Show how fluids like water boil when they are

exposed to a vacuum. Place water in a beaker and

evacuate the bell jar. The demonstration will take

place more rapidly if warm water is used. Place a

thermometer in the beaker to record the boiling

temperature.

11. Vacuum Experiment - 3

C on s t ruct a marshmall ow astronaut out of re g ular size and mini marshmall ows and toothpick s .

Evacuate the bell jar and observe how the marshm a ll ows expand. Living tissue will also inflate in

a vacuum because of gas bubbles forming in the

fluids of cell s .

Note: The vacuum pump, vacuum plate, and bell jar

needed for the activities on this page are common pieces

of science equipment found in many junior and senior

high schools. This equipment is available from school

science supply catalogs.

12.Underwater Training

If a swimming pool is available, practice underwa -

ter EVA training. Have students wear a dive mask

9 2 • Suited for Spacewalking An Activity Guide for Technology Education, Mathematics, and Science, EG- 1 9 9 8 - 0 3 - 1 1 2 - H Q

To Transformer

Push

Button

Doorbell
and assemble PVC water pipe parts underwater.

Make a weighted panel that has bolts protruding

from it.Use a chrome steel wrench to try to turn the

bolts while free floating in the water. Make tools

appear weightless by attaching a string to the handles and to empty two liter soft drink bottles.Invite

a local SCUBA shop to participate in the activity.

The shop owners might be willing to supply dive

equipment and serve as safety divers during the

simulation.

13.Design A Tool

Have students design and construct a prototype

multipurpose tool for use on spacewalks. The tool

should combine the functions of single purpose

tools such as hammers,screw drivers, wrenches,etc.

The tool should also make provisions for attachment to tethers and easy gripping.

14. Torque

Place a student on a swivel office chair or on a

rotating platform like a child's Sit and Spin®. Have

two other students hold a 2 by 4, with a bolt partially screwed into it, over the first student.The first

student will find it difficult to turn the bolt with a

wrench without spinning as well. Relate this to the

challenges astronauts have on spacewalks when

they try to do a similar job. To turn a bolt or move

s ome massive object in space, an astronaut is

attached to a stable work platform.

15.Glove Work

Use rubber-coated work gloves from a hardware

store to demonstrate the importance of spacesuit

gloves that are comfortable to wear. Have students

attempt to screw a bolt into a nut or assemble plastic snap toys into a structure. Discuss how these

gloves can be improved to make them easier to use.

16. Neutral Buoyancy

A s t ronauts simulate micro g ra v i ty for spacesuit

training in a deep swimming pool.Their spacesuits

are specially weighted to produce neutral buoyanc y.

Suited for Spacewalking An Activity Guide for Technology Education, Mathematics, and Science, EG-1998-03-112-HQ • 9 3
You can investigate neutral buoyancy by creating a

small submarine out of a plastic film canister,

aquarium tubing, pennies, and hot glue. Punch tow

holes at the base of the canister and a hole in the lid.

Hot glue the end of the aquarium tube into the hole

in the lid. Add several pennies to the canister so

that when you place it in a water-filled aquarium,

the canister just floats. Suck air out of the tube to

cause the canister to sink. Try to get the canister to

hover half way from the bottom to the surface.

17. Neutral Buoyancy - 2

Neutral buoyancy can also be investigated with a

Cartesian diver. Fill a plastic soft drink bottle with

water. Insert an eyedropper that is partially filled

with water. Cap the bottle and squeeze the bottle's

sides to increase the pressure in the bottle. The

trapped air in the eyedropper will compress and the

eye dropper will sink. Try to get the eyedropper to

hover midway in the bottle.

9 4 • Suited for Spacewalking An Activity Guide for Technology Education, Mathematics, and Science, EG- 1 9 9 8 - 0 3 - 1 1 2 - H Q
Suited for Spacewalking An Activity Guide for Technology Education, Mathematics, and Science, EG-1998-03-112-HQ • 9 5

AMU Astronaut Maneuvering Unit

Apollo NASA project that landed astronauts on the Moon

CCA Communications Carrier Assembly

CCC Contaminant Control Cartridge

Composite Material Substance derived by combining two or more

materials such as glass fibers and epoxy

DCM Displays and Control Module

EEH EMU Electrical Harness

EMU Extravehicular Mobility Unit

EVA Extravehicular Activity; Extravehicular Visor 

Assembly

Gemini NASA project that pioneered space flight 

technologies for spacecraft rendezvous and docking 

and spacewalking

HHMU Hand-Held Maneuvering Unit

HUT Hard Upper Torso

IDB In-Suit Drink Bag 

ISS International Space Station

Joule One newton meter or 1 kg • m2/s2

Kilopascal Metric pressure unit; one pound per square inch

pressure equals 6.895 kilopascals

Kinetic Energy Energy in motion

LCVG Liquid Cooling-and-Ventilation Garment

MAG Maximum Absorption Garment

Microgravity An env i ron m e n t , p roduced by fre e - f a ll , that alters the

l o cal effects of gra v i ty and makes objects seem weightless

Micrometeoroid Ti ny part i cle of space debris (natural or art i f i c i a l )

ravling at high speed through space

Gl o s s a ry
9 6 • Suited for Spacewalking An Activity Guide for Technology Education, Mathematics, and Science, EG- 1 9 9 8 - 0 3 - 1 1 2 - H Q

MMU Manned Maneuvering Unit

Mercury The NASA project that launched the first U.S.

astronauts into space and demonstrated that humans 

could live and work in space

ORU Orbital replacement unit

PLSS Primary Life-Support System

Regolith Sediment derived directly from igneous rock and not 

containing any organically-derived materials

RMS Remote Manipulator System

SCU Service and Cooling Umbilical

Skylab First U.S. space station

SOP Secondary Oxygen Pack

SAFER Self-rescue rocket backpack device for use during 

spacewalks around the International Space Station

Space Shuttle Reusable spaceship currently used for all U.S. manned 

space missions

Spacewalk Extravehicular activity

Sublimation Change of state of matter from a solid to a gas
Suited for Spacewalking An Activity Guide for Technology Education, Mathematics, and Science, EG-1998-03-112-HQ • 9 7

A ll e n , J. P. with Mart i n ,M .( 1 9 8 4 ) , E n tering Spac e, An

As tro n au t’s Odyssey, St ew a rt , Ta b o ri & Chang,

New Yo rk City, N Y.

C om p t on , W. & Bensen, C . ( 1 9 8 3 ) , L iving and

Wo rking In Spac e, A Hi s t o ry of S k y l a b, NASA SP4 2 0 8 , Scientific and Te ch n i cal Inform a t i on

B ra n ch ,NASA Headquart e r s ,Wa s h i n g t on ,DC .

K o z l o s k i , L . ( 1 9 9 4 ) , U. S . S p ace Gear, O u tfitting T h e

As tro n au t, Sm i t h s onian Institution Pre s s ,

Wa s h i n g t on , DC .

Ku z n i k , F. ( 1 9 9 7 ) , Spacesuit Sa g a : A St o ry in Many

Pa rt s , Air & Sp a c e, V 1 2 N 3 .

M a ch e ll , R. e d . ( 1 9 6 7 ) , S u m m a ry of G e m i n i

E x travehicular Activ i ty, NASA SP-149,

Scientific and Te ch n i cal Inform a t i on Division ,

Office of Te ch n o l o gy Ut i l i za t i on , NA S A

H e a d q u a rt e r s , Wa s h i n g t on , DC .

M oh l e r, S. R. & Joh n s on , B. H .( 1 9 7 1 ) , Wi l ey Po s t , Hi s

Winnie Mae, and the Wo rl d’s First Pre s s u re Suit,

Sm i t h s onian Institution Pre s s ,Wa s h i n g t on , DC .

NASA (1973),Ap o l l o, EP - 1 0 0 , NASA Headquart e r s ,

Wa s h i n g t on , DC .

NASA (1991), Go For EVA, L i ftoff to Le a rn i n g

Se ri e s . (Vi d e o t a p e ) ,E d u ca t i on Wo rking Gro u p,

NASA Joh n s on Space Center, H o u s t on , TX .

NASA (1987), The Early Ye a r s : M erc u ry to Ap o l l o -

S oy u z, I n f o rm a t i on Su m m a ri e s , PMS 001-A,

NASA Kennedy Space Center, F L .

NASA (1970), The First Lunar Landing As Told by

The As tro n au t s, EP - 7 3 , NASA Headquart e r s ,

Wa s h i n g t on , DC .

Vo g t , G . ( 1 9 8 7 ) , S p ac ew a l k i n g, Franklin Wa t t s , New

Yo rk City, N Y.

Vo g t , G . , R o d g e r s , M . and Wa r go, M . ( 1 9 9 7 ) ,

M i c ro grav i ty - A Te ach er's Guide With Activ i t i e s ,

S e c o n d a ry Level, E G - 1 9 9 7 - 0 8 - 1 1 0 - H Q , NA S A

H e a d q u a rt e r s , Wa s h i n g t on , DC .

Re f e r e n c e s
Suited for Spacewalking An Activity Guide for Technology Education, Mathematics, and Science, EG-1998-03-112-HQ • 9 9

NA S A’s Central Ope ra tion of Resources for Ed u ca t o r s

(CORE) was established for the national and international distribution of NASA-produced educational materials in audiovisual format.Educators can obtain a catalogue and an order form

by one of the following methods:

• NASA CORE

Lorain County Joint Vocational School

15181 Route 58 South

Oberlin,OH 44074

• Phone (440) 774-1051, Ext.249 or 293

• Fax (440) 774-2144

• E-mail nasaco@leeca8.esu.k12.oh.us

• Home Page: http://spacelink.nasa.gov/CORE

Educator Resource Center Network

To make additional inform a t i on available to the educa t i on commu n i ty, the NASA Educa t i on Division has created the NA S A

E d u cator Resource Center (ERC) netw o rk . ERCs contain a

wealth of inform a t i on for educa t o r s : p u b l i ca t i on s , re fe re n c e

b o ok s , slide sets, audio ca s s e t t e s ,v i d e o t a p e s ,t e l e l e c t u re pro g ra m s ,

c omputer pro g ra m s ,l e s s on plans, and teacher guides with activit i e s .E d u cators may prev i ew, c o p y, or re c e i ve NASA materials at

these sites. B e cause each NASA Field Center has its own areas of

e x p e rt i s e, no two ERCs are exactly alike. Ph one ca lls are welcom e

if you are unable to visit the ERC that serves your geogra ph i c

a re a . A list of the centers and the re g i ons they serve incl u d e s :

Regional Ed u cator Resource Centers o f fer more educators access

to NASA educa t i onal materi a l s . NASA has formed part n e r s h i p s

with unive r s i t i e s , mu s e u m s , and other educa t i onal institutions to

s e rve as re g i onal ERCs in many states. A complete list of re g i on a l

ERCs is available through CO RE , or electron i ca lly via the NA S A

E d u ca t i on Home Page at: h t t p : / / w w w. h q. n a s a . go v / e d u ca t i o n

NASA On-line Resources for Ed u ca t o r s p rovide current educa t i onal inform a t i on and instru c t i onal re s o u rce materials to

t e a ch e r s , f a c u l ty, and students. A wide range of inform a t i on is

a v a i l a b l e, i n cluding science, m a t h e m a t i c s , e n g i n e e ri n g, a n d

t e ch n o l o gy educa t i on lesson plans, h i s t o ri cal inform a t i on re l a ted to the ae ronautics and space pro g ra m , c u r rent status re p o rt s

on NASA pro j e c t s , n ews re l e a s e s , i n f o rm a t i on on NASA educa t i onal pro g ra m s , useful softw a re and gra phics files. E d u ca t o r s

and students can also use NASA re s o u rces as learning tools to

e x p l o re the Intern e t , accessing inform a t i on about educa t i on a l

g ra n t s ,i n t e racting with other schools which are already on - l i n e,

and participating in on-line intera c t i ve pro j e c t s ,c om mu n i ca t i n g

with NASA scientists, e n g i n e e r s , and other team members to

e x p e rience the excitement of real NASA pro j e c t s .

Access these resources through the NASA Education Home

Page: http://www.hq.nasa.gov/education

NASA Television (NTV) is the Agency's distribution system for

live and taped programs.It offers the public a front-row seat for

launches and missions, as well as informational and educational

programming, historical documentaries,and updates on the latest developments in aeronautics and space science.NTV is transmitted on the GE-2 satellite, Transponder 9C at 85 degrees

West longitude, vertical polarization, with a frequency of 3880

megahertz,and audio of 6.8 megahertz.

Ap a rt from live mission cove ra g e, regular NASA Te l ev i s i on prog ramming includes a Video File from noon to 1:00 pm , a NA S A

G a ll e ry File from 1:00 to 2:00 pm , and an Educa t i on File from

2:00 to 3:00 pm (all times Eastern ) . This sequence is repeated at

3:00 pm , 6:00 pm , and 9:00 pm , M on d ay through Fri d ay. T h e

N TV Educa t i on File fe a t u res pro g ramming for teachers and 

students on science, m a t h e m a t i c s , and tech n o l o gy. NA S A

Te l ev i s i on pro g ramming may be videotaped for later use.

For more information on NASA Television,contact:

NASA Headquarters, Code P-2, NASA TV, Washington, DC

20546-0001 Phone:(202) 358-3572 

NTV Home Page: http://www.hq.nasa.gov/ntv.html

How to Access NASA's Education Materials and Services,

EP-1996-11-345-HQ

This bro ch u re serves as a guide to accessing a vari e ty of NA S A

m a t e rials and services for educa t o r s . Copies are available

t h rough the ERC netw o rk , or electron i ca lly via NA S A

Sp a c e l i n k . NASA Spacelink can be accessed at the foll ow i n g

a d d re s s : h t t p : / / s p ac el i n k . n a s a . go v

NASA Resources for Educators

AK, AZ, CA,HI,ID, MT, NV, OR, UT,

WA,WY

NASA Educator Resource Center

Mail Stop 253-2

NASA Ames Research Center

M o f fett Fi e l d , CA 94035-1000

Ph on e : (415) 604-3574

CT, D E ,D C ,M E ,M D, M A ,N H , N J, N Y,

PA ,RI ,VT

NASA Educator Resource La b o ra t o ry

Mail Code 130.3

NASA Goddard Space Flight Center

G re e n b e l t , MD 20771-0001

Ph on e : (301) 286-8570

CO ,K S ,N E ,N M ,N D, O K ,S D, TX

JSC Educator Resource Center

Space Center Houston

NASA Johnson Space Center

1601 NASA Road One

H o u s t on ,TX 77058-3696

Ph on e : (281) 483-8696

F L ,G A ,P R,V I

NASA Educator Resource La b o ra t o ry

Mail Code ER L

NASA Kennedy Space Center

Kennedy Space Center, FL 32899-0001

Ph on e : (407) 867-4090

KY, N C ,S C ,VA ,W V

Virginia Air and Space Museum

NASA Educator Resource Center for

NASA Langley Research Center

600 Settlers Landing Road

H a m p t on , VA 23669-4033

Ph on e : (757) 727-0900 x 757

I L ,I N ,M I ,M N ,O H ,W I

NASA Educator Resource Center

Mail Stop 8-1

NASA Lewis Research Center

21000 Bro ok p a rk Road

C l eve l a n d , OH 44135-3191

Ph on e : (216) 433-2017

A L ,A R,I A , LA ,M O ,TN

U. S. Space and Rocket Center

NASA Educator Resource Center for 

NASA Marshall Space Flight Center

P. O. B ox 070015

H u n t s v i ll e, AL 35807-7015

Ph on e : (205) 544-5812

M S

NASA Educator Resource Center

Building 1200

NASA John C. Stennis Space Center

Stennis Space Center, MS 39529-6000

Ph on e : (601) 688-3338

NASA Educator Resource Center

JPL Educa t i onal Ou t re a ch

Mail Stop CS-530

NASA Jet Propulsion Labora t o ry

4800 Oak Grove Dri ve

Pa s a d e n a , CA 91109-8099

Ph on e : (818) 354-6916

CA cities near the Center

NASA Educator Resource Center for

NASA Dryden Flight Research Center

45108 N. 3 rd St reet East

La n ca s t e r, CA 93535

Ph on e : (805) 948-7347

VA and MD's Eastern Shore s

NASA Educator Resource La b

E d u ca t i on Complex - Visitor Center

Building J-1

NASA Wa llops Flight Fa c i l i ty

Wa llops Island, VA 23337-5099

Ph on e : (757) 824-2297/2298
Suited for Spacewalking An Activity Guide for Technology Education, Mathematics, and Science, EG-1998-03-112-HQ • 1 0 1

Go For EVA ! is from the L i f t o f f to Learn i n g

E d u cational Vi d e o tape Seri e s, w h i ch all ows students to

study science, m a t h e m a t i c s , and tech n o l o gy with

c rew members aboard Space Shuttle flights.

Go For EVA ! discusses how spacesuits protect astronauts from the hostile space env i ron m e n t , e x p l a i n s

what the com p onents of the spacesuit are, d e s c ri b e s

h ow the suit function s , and shows what types of work

a s t ronauts perf o rm while spacew a l k i n g. Ac t u a l

footage of spacewalks–also known as Extra ve h i c u l a r

Activities (EVA s ) – i ll u s t rate how spacesuits all ow

a s t ronauts to operate scientific appara t u s , a s s e m b l e

e q u i pment and stru c t u re s , pilot the Manned

M a n e u ve ring Unit, take picture s , and service satellites and space hard w a re .

Length: 13:48

To obtain a copy of the Go For EVA ! videotape and

a c c om p a nying Video Resource Gu i d e, or for more

i n f o rm a t i on on the L i f t o f f to Learning Educa t i o n a l

Vi d e o tape Seri e s, c ontact your local Educator Resourc e

Center or the NASA Central Opera t i on of Resourc e s

for Educators (CO RE ) . See page 99 for details.

Go For EVA!

Educational Videotape Series

Grade Level Application

K–8

Technology Education,

Life Sciences, Physical

Science, History 

Image from the videotape Go for EVA! ofthe Liftoff To Learning

Videotape Series.
Suited for Spacew a l k i n g

A Te a c h e r’s Guide with Activities for Te c h n o l o g y

Education, Mathematics, and Science

T E ACHER REPLY CARD

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